Transcript Anemias Definition • Reduction of total RBC MASS below average levels • Reduction of oxygen carrying capacity of the blood • Leads to tissue hypoxia •

Anemias
Definition
• Reduction of total RBC MASS below average
levels
• Reduction of oxygen carrying capacity of the
blood
• Leads to tissue hypoxia
• Practically, measure by Hemoglobin
concentration, and Hematocrit (ratio of packed
RBCs to total blood volume). They correlate well
with anemia when the plasma volume is normal
Classification of anemia
according to cause
• Blood loss: acute, chronic
• Diminished RBC production
• Increased destruction (hemolytic anemia)
• Extrinsic factors (infection, antibody, mechanical)
• Intrinsic RBC abnormalities:
1) Hereditary (membrane, enzyme, Hg
abnormalities)
2) Acquired (Paroxysmal nocturnal hematuria)
Classification of anemia
•
•
•
•
According to morphology:
Size: normo, micro, macrocytic
Color: normo, hypochromic
Shape: anisopoikelocytosis (spherocytes, sickle,
schistiocytes)
• Hypochromic microcytic anemia usually reflects
impaired Hg synthesis
• Macrocytic anemia reflects stem cell disease and
maturation
RBC indices
• Hg concentration, Men: 13.8-18.0 g/dL, Women: 12-15
• Hematocrit: volume % of RBCs in blood, 45% men, 40% women
• Mean Cell Volume (MCV): average size in femtoliter, 10−15 (normal:
80-99 fL)
• Mean Cell Hg (MCH): average mass of Hg inside the RBC in
picograms, 10−12, normal (27-31)
• Mean Cell Hg Concentration (MCHC): the average concentration of
Hg in a given volume of packed red cells, expressed in grams per
deciliter
• RBC count: number of cells/L Male: 4.7-6.1 million/ microliter
Female: 4.2-5.4
• Reticulocyte index (0.5-1.5%)
• Red cell distribution width (RDW): the coefficient of variation in red
cell volume
Clinical features of anemia
•
•
•
•
•
•
•
•
Dizziness
Fatigue
Pallor
Headache
Hypotension
Tachycardia
Dyspnea
Special types: jaundice, bone and joint pain,
growth retardation
Anemia of acute blood loss
• Symptoms are related to decreased intravascular volume, might
cause cardiovascular shock and death
• Body responds by shifting fluid from interstitial to intravascular
space, causing dilutional anemia and hypoxia
• Erythropoietin secretion is stimulated, activating BM erythropoiesis
• Mature RBCs as well as Reticulocytes appear in blood after 5 days
• In internal hemorrhage, iron is restored from extravasated RBCs and
used again in erythropoiesis
• In external and GIT hemorrhage, iron is lost, which complicated
anemia
• The anemia is normochromic normocytic, with reticulocytosis
• Leukocytosis (secondary to stress)
• Thrombocytosis (secondary to high erythropoietin)
Anemia of chronic blood loss
• Occurs when the rate of RBC loss exceeds
regeneration
• Mostly associated with iron deficiency anemia
Hemolytic Anemia
• Normally, RBCs age is around 120 days, aged RBCs
are engulfed by phagocytic cells in spleen, liver and
BM
• In Hemolytic anemia; premature destruction of
RBCs
• Accumulation of Hg degradation products
• Secondary increased erythropoiesis
• Extravascular hemolysis: increased phagocytic
activity
• Intravascular hemolysis: occurs inside blood vessels
Extravascular Hemolysis
• Generally caused when the RBC is less deformable or
having abnormal shape
• Abnormal RBC shape prevents its normal movement in
splenic sinusoids
• Prolonged time of RBCs passage attracts histiocytes to
engulf them
• Free Hg from destructed RBCs binds Haptoglobin in
serum
• Hg within phagocytes is converted to bilirubin
• The triad of extravascular HA is: Anemia, splenomegaly
and jaundice
Intravascular Hemolysis
• Less common
• Caused by mechanical damage, complement
fixation, microorganism, exogenous toxins
• Due to large amount of free Hg, haptoglobin is
cleared from the serum
• free Hg in serum is oxidized to Methemoglobin
(metHg),
• Excess free Hg and met Hg are excreted in urine
(hemoglobinuria) causing dark urine
• Renal hemosiderosis may occur
Hereditary Spherocytosis
• This inherited disorder is caused by intrinsic defects in
the red cell membrane skeleton that render red cells
spheroid, less deformable, and vulnerable to splenic
sequestration and destruction
• The prevalence of HS is highest in northern Europe
• AD inheritance pattern, in 75% of cases
• The remaining patients have a more severe form of the
disease that is usually caused by the inheritance of two
different defects (a state known as compound
heterozygosity)
Pathophysiology
• Normal RBC is durable and elastic
• Spectrin is the major internal membrane protein,
consists of two helical polypeptides; α, β
• The tail of Spectrin binds Actin
• Spectrin-Actin complex, is connected by Ankyrin
and band 4.2 to band 3, a transmembrane
protein
• Protein 4.1 binds the tail of spectrin to
Glycophorin A, a transmembrane protein
Pathophysiology
• Various mutations involving α-spectrin, β-spectrin, ankyrin, band
4.2, or band 3 that weaken the interactions between these proteins
cause red cells to lose membrane fragments
• Most mutations are frame-shift, resulting in absent protein
• To accommodate the resultant change in the ratio of surface area to
volume these cells adopt an irreversible spherical shape
• Spherocytic cells are less deformable than normal ones and
therefore become trapped in the splenic cords, where they are
phagocytosed by macrophages
• Na+ influx in spherocytes is twice than normal, while K+ efflux is the
same, facilitating hemolysis in the microenvironment of the spleen
• RBC Life span is dropped to less than 20 days
Clinical features
• Congestion of RBCs in the spleen causes
splenomegaly and anemia
• Jaundice, pigmented gall bladder stones
• Reticulocytosis, BM erythroid hyperplasia,
hemosiderosis
• Family Hx of anemia or splenectomy
• Abnormal osmotic fragility test
• Increased MCHC in 50% of cases
• Treatment: splenectomy
Morphology
• Blood film: RBCs are round, small,
hyperchromatic, no visible central pallor
• “Howell-Jolly” bodies are seen in post
splenectomy. A fragment of chromosome
which is detached and left in the cytoplasm
after the extrusion of the nucleus, secondary
to accelerated erythropoiesis. Appears as 1 or
2 eccentric dots
Spherocytes appear as small, round cells without the central pallor. Howell
Jolly bodies are noted
Glucose-6-Phosphate Dehydrogenase Deficiency
• G6PD reduces nicotinamide adenine dinucleotide
phosphate (NADP) to NADPH while oxidizing
glucose-6-phosphate
• NADPH then provides reducing equivalents
needed which protects against oxidant injury by
catalyzing the breakdown of compounds such as
H 2O 2
• G6PD deficiency is a recessive X-linked trait,
placing males at higher risk for symptomatic
disease.
Types of G6PD deficiency
• Several hundred G6PD genetic variants are
known, but most are harmless
• The normal enzyme is G6PD-B
• Only two variants, designated G6PD-A and
G6PD Mediterranean, cause most of the
clinically significant hemolytic anemias
• G6PD-A is present in about 10% of American
blacks; G6PD Mediterranean is prevalent in
the Middle East
Pathophysiology
• The half-life of G6PD-A is moderately reduced,
whereas that of G6PD Mediterranean is
functionally abnormal
• Because mature red cells do not synthesize
new proteins, G6PD-A or G6PD Mediterranean
enzyme activities fall quickly to levels
inadequate to protect against oxidant stress as
red cells age. Thus, older red cells are much
more prone to hemolysis than younger ones
Pathophysiology
• Oxidants cause both intravascular and extravascular hemolysis in
G6PD-deficient individuals
• Exposure of G6PD-deficient red cells to high levels of oxidants
causes the cross-linking of reactive sulfhydryl groups on globin
chains, which become denatured and form membrane-bound
precipitates known as Heinz bodies
• These are seen as dark inclusions within red cells stained with
crystal violet. Heinz bodies can damage the membrane
sufficiently to cause intravascular hemolysis
• Splenic macrophages identify Heinz bodies and pluck them out
resulting in indentation. The remaining RBC is known as “bite
cells”
Causes of hemolytic crisis
• Hemolysis happens upon exposure to oxidant stress
• The most common triggers are infections, in which oxygen-derived
free radicals are produced by activated leukocytes
• Many infections can trigger hemolysis; viral hepatitis, pneumonia,
and typhoid fever
• The other important initiators are drugs and certain foods
• Most important drugs are the antimalarials (e.g., primaquine and
chloroquine), sulfonamides, nitrofurantoins
• Some drugs cause hemolysis only in individuals with the more
severe Mediterranean variant.
• The most frequently cited food is the fava bean (Favism)
• Uncommonly, G6PD deficiency presents as neonatal jaundice or a
chronic low-grade hemolytic anemia in the absence of infection or
known environmental triggers
Clinical features
• Majority of patients are asymptomatic, anemia develops
when the enzyme level drops below 20% of normal activity
• Hemolytic crisis appear 2-3 days after exposure to oxidant
• Only old RBCs hemolize, HB level drops, RBCs appear
normochromic normocytic, patients have bone pain
• Chronic hemolysis (splenomegaly and GB stones) are
absent
• G6PD-A usually is self-limited
• G6PD-Mediterranian has more severe crisis, might need
blood transfusion
• Recovery is associated with reticulocytosis
• Dx: enzyme assay (measure conversion to NAPDH)
Pyrovate kinase deficiency
• AR inheritance
• PK is an enzyme in the anaerobic glycolysis pathway
(main pathway in RBCs)
• PK deficiency causes decreased ATP level which is
essential for cell membrane pumps
• Intracellular Na accumulates, causing swelling of RBCs
and rigidity
• Spleen clears abnormal shaped RBCs
• 2,3 diphosphoglycerate (DPG) level increases inside
RBCs, facilitating O2 release, ameliorating the anemia
Clinical
• Degree of anemia varies according to type of
mutation, ranging from neonatal jaundice to
anemia presenting in adulthood with
jaundice, GB stones and splenomegaly
• Anemia is exacerbated by stress
• Blood film shows NN anemia, variable
reticulocytosis, anisopoikelocytosis
• Diagnosis: enzyme assay
• Treatment: splenectomy
Paroxysmal Nocturnal Hematuria
• Acquired disease
• Normally, proteins are anchored into the lipid bilayer in two ways.
Most have a hydrophobic region that spans the cell membrane;
these are called transmembrane proteins. The others are attached
to the cell membrane through a covalent linkage to a specialized
phospholipid called glycosylphosphatidylinositol (GPI)
• In PNH, there is a mutation in the phosphatidylinositol glycan
complementation group A gene (PIGA), which synthesizes GPI
• Thus, GPI and their normally anchored proteins are absent
• Because the causative mutations occur in a hematopoietic stem
cell, all of its clonal progeny (red cells, white cells, and platelets) are
deficient in GPI-linked proteins
Patholophysiology
• Normal individuals harbor small numbers of bone
marrow cells with PIGA mutations
• In PNH, autoimmune reaction occurs against normal
clones resulting in predominance of GPI-deficient clone
• PNH blood cells are deficient in three GPI-linked
proteins that regulate complement activity: (1) decayaccelerating factor, or CD55; (2) membrane inhibitor of
reactive lysis, or CD59; and (3) C8 binding protein. Of
these factors, the most important is CD59, a potent
inhibitor of C3 convertase that prevents the
spontaneous activation of the alternative complement
pathway
Clinical features
• Red cells, platelets, and granulocytes deficient in these GPI-linked factors
are abnormally susceptible to lysis or injury by complement. In red cells
this manifests as intravascular hemolysis, which is caused by the C5b-C9
membrane attack complex
• The hemolysis is intravascular, paroxysmal and nocturnal in only 25% of
cases; chronic hemolysis without dramatic hemoglobinuria is more typical.
The tendency for red cells to lyse at night is explained by a slight decrease
in blood pH during sleep, which increases the activity of complement
• Thrombosis is the leading cause of death in PNH. About 40% of patients
suffer from venous thrombosis, often involving the hepatic, portal, or
cerebral veins. Autolysis of some platelets causes aggregation of others
secondary to released prothrombotic factors
• In severe cases, pancytopenia develops
• About 5% to 10% of patients eventually develop acute myeloid leukemia
or a myelodysplastic syndrome, possibly because hematopoietic stem cells
have suffered some type of genetic damage.
Autoimmune hemolytic anemia
• A group of anemias in which an abnormal immunoglobulin
is attached to RBC membrane causing damage and lysis
• Direct Coombs antiglobulin test: the patient's RBCs are
mixed with sera containing antibodies that are specific for
human immunoglobulin. If either immunoglobulin is
present on the surface of the red cells, the multivalent
antibodies cause agglutination, which is easily appreciated
visually as clumping
• Indirect Coombs antiglobulin test, the patient's serum is
tested for its ability to agglutinate commercially available
red cells bearing particular defined antigens
Warm Antibody Type
• 70% of immunohemolytic anemia.
• 50% are idiopathic (primary); the others are related to a
predisposing condition or exposure to a drug.
• Most causative antibodies are of the IgG class; less commonly,
IgA antibodies
• A common target is the Rh antigen on RBCs
• The red cell hemolysis is mostly extravascular. IgG-coated red
cells bind to Fc receptors on phagocytes, which remove red
cell membrane during "partial" phagocytosis. As in hereditary
spherocytosis, the loss of membrane converts the red cells to
spherocytes, which are sequestered and removed in the
spleen. Moderate splenomegaly due to hyperplasia of splenic
phagocytes is usually seen
Drug induced hemolytic anemia
• Antigenic drugs. In this setting hemolysis usually follows large, intravenous
doses of the offending drug and occurs 1 to 2 weeks after therapy is
initiated. These drugs, like penicillin and cephalosporins, bind to the red
cell membrane and are recognized by anti-drug antibodies. Sometimes the
antibodies bind only to the drug, as in penicillin-induced hemolysis. In
other cases, such as in quinidine-induced hemolysis, the antibodies
recognize a complex of the drug and a membrane protein. The responsible
antibodies sometimes fix complement and cause intravascular hemolysis,
but more often they act as opsonins that promote extravascular hemolysis
within phagocytes
• Tolerance-breaking drugs. These drugs, of which the antihypertensive
agent α-methyldopa is the prototype, induce in some unknown manner
the production of antibodies against red cell antigens, particularly the Rh
blood group antigens. About 10% of patients taking α-methyldopa develop
autoantibodies, as assessed by the direct Coombs test, and roughly 1%
develop clinically significant hemolysis
Cold Agglutinin Type
•
•
•
This form of immunohemolytic anemia is caused by IgM antibodies that bind red
cells avidly at low temperatures (0°-4°C). It is less common than warm antibody
immunohemolytic anemia, accounting for 15% to 30% of cases
Cold agglutinin antibodies sometimes appear transiently following certain
infections, such as with Mycoplasma pneumoniae, Epstein-Barr virus,
cytomegalovirus, influenza virus, and human immunodeficiency virus (HIV). In
these settings the disorder is self-limited and the antibodies rarely induce clinically
important hemolysis. Chronic cold agglutinin immunohemolytic anemia occurs in
association with certain B-cell neoplasms or as an idiopathic condition.
Clinical symptoms result from binding of IgM to red cells in vascular beds where
the temperature may fall below 30°C, such as in exposed fingers, toes, and ears.
IgM binding agglutinates red cells and fixes complement rapidly. As the blood
recirculates and warms, IgM is released, usually before complement-mediated
hemolysis can occur. However, the transient interaction with IgM is sufficient to
deposit sublytic quantities of C3b, an excellent opsonin, which leads to the
removal of affected red cells by phagocytes in the spleen, liver, and bone marrow.
The hemolysis is of variable severity
• RBC agglutination in autoimmune hemolytic anemia
Cold Hemolysin Type
• Cold hemolysins are autoantibodies responsible for an
unusual entity known as paroxysmal cold hemoglobinuria
• This rare disorder causes substantial, sometimes fatal,
intravascular hemolysis and hemoglobinuria
• The autoantibodies are IgGs that bind to the P blood group
antigen on the red cell surface in cool, peripheral regions of
the body. Complement-mediated lysis occurs when the
cells recirculate to warm central regions, since the
complement cascade functions more efficiently at 37°C
• Most cases are seen in children following viral infections; in
this setting the disorder is transient, and most of those
affected recover within 1 month.
Hemolytic Anemia Resulting from
Trauma to Red Cells
• Physical damage to RBCs
• Cardiac valve prosthesis
• Microangiopathic disease (disseminated
intravascular coagulation DIC, thrombotic
thrombocytopenic purpura (TTP), hemolyticuremic syndrome (HUS), malignant hypertension,
systemic lupus erythematosus, and disseminated
cancer): aggregates of fibrin and platelets causes
damage to RBCs
• RBCs appear as fragments (schistocytes)
Schistocytes
Hemoglobinopathies
Normal Hemoglobin Structure
• Two pairs of globin chains with a haem group
attached.
• 7 chains are synthesized in normal subjects: 4
embryonic: Hg Gower 1,2 Hg Portland 1,2. Hg F
(fetal), Hg A, Hg A2
• The individual chains synthesized in postnatal life
are designated α, β, γ, and δ
• Hg A has two α chains and two β chains (α2 β2)
• Hg A2 has two α chains and two δ chains (α2 δ2),
1.5-3%
• Hg F has two α chains and two γ chains (α2 γ2),
1%
Genes controling Hg synthesis
* α Chain synthesis is directed by two α genes, α 1 and α 2,
on chromosome 16
* β and δ chain synthesis by single β and δ genes on
chromosome 11
* γ Chain synthesis is directed by two genes, Gγ and Aγ,
also on chromosome 11
Thalassemia
• The thalassemia syndromes are a heterogeneous group of
disorders caused by inherited mutations that decrease the
synthesis of adult hemoglobin, HgA (α2β2)
• Endemic in Middle East, tropical Africa, India, Asia
• β-Thalassemia is caused by deficient synthesis of β chains,
whereas α-thalassemia is caused by deficient synthesis of α
chains
• The hematologic consequences of diminished synthesis of one
globin chain stem not only from hemoglobin deficiency but
also from a relative excess of the other globin chain,
particularly in β-thalassemia
β-Thalassemias
• caused by mutations that diminish the
synthesis of β-globin chains
• β0 mutations, associated with absent β-globin
synthesis
• β+ mutations, characterized by reduced (but
detectable) β-globin synthesis
• 100 different causative mutations, mostly
consisting of point mutations
Types of mutations
• Splicing mutations: most common cause of β+-thalassemia. Most of these
mutations lie within introns, while a few are located within exons. Some of
these mutations destroy the normal RNA splice junctions and completely
prevent the production of normal β-globin mRNA, resulting in β0thalassemia
• Promoter region mutations. These mutations reduce transcription by 75%
to 80%. Some normal β-globin is synthesized; thus, these mutations are
associated with β+-thalassemia.
• Chain terminator mutations. These are the most common cause of β0thalassemia. Two subtypes of mutations fall into this category. The most
common type creates a new stop codon within an exon; the second
introduces small insertions or deletions that shift the mRNA reading
frames, Both block translation and prevent the synthesis of any functional
β-globin
Pathophysiology
• The deficit in HgA synthesis produces "underhemoglobinized"
hypochromic, microcytic red cells with subnormal oxygen
transport capacity
• Diminished survival of red cells and their precursors, which
results from the imbalance in α- and β-globin synthesis.
Unpaired α chains precipitate within red cell precursors, forming
insoluble inclusions, which damage cell membrane and results in
cell death in RBC precursors (Ineffective erythropoiesis)
• Those red cells that are released from the marrow also bear
inclusions and membrane damage and are prone to splenic
sequestration and extravascular hemolysis
Pathophysiology
• In severe β-thalassemia, uncompensated anemia leads to massive
erythroid hyperplasia in the marrow and extensive extramedullary
hematopoiesis in spleen, liver and LNs
• The expanding mass of red cell precursors erodes the bony cortex,
impairs bone growth, and produces skeletal abnormalities
• The metabolically active erythroid progenitors steal nutrients from
other tissues that are already oxygen-starved, causing severe
cachexia in untreated patients.
• Ineffective erythropoiesis suppresses the circulating levels of
hepcidin, a critical negative regulator of iron absorption. Low levels
of hepcidin and the iron load of repeated blood transfusions
inevitably lead to severe iron overload
Clinical syndromes
• In general, individuals with two β-thalassemia alleles (β+/β+,
β+/β0, or β0/β0) have a severe, transfusion-dependent anemia
called β-thalassemia major
• Heterozygotes with one β-thalassemia gene and one normal
gene (β+/β or β0/β) usually have a mild asymptomatic
microcytic anemia. This condition is referred to as βthalassemia minor or β-thalassemia trait
• A third genetically heterogeneous variant of moderate
severity is called β-thalassemia intermedia. This category
includes milder variants of β+/β+ or β+/β0-thalassemia and
unusual forms of heterozygous β-thalassemia
α-thalassemia
• Normally, there are four α-globin genes, and the severity of α-thalassemia
depends on how many α-globin genes are affected
• As in β-thalassemias, the anemia occurs both from inadequate
hemoglobin synthesis and the effects of excess unpaired non-α chains (β,
γ, and δ)
• In newborns with α-thalassemia, excess unpaired γ-globin chains form
γ4 tetramers known as hemoglobin Barts, whereas in older children and
adults excess β-globin chains form β4 tetramers known as HgH.
• Since free β and γ chains are more soluble than free α chains, hemolysis
and ineffective erythropoiesis are less severe than in β-thalassemias.
• Gene deletion is the most common cause of reduced α-chain synthesis.
Clinical features
• Silent carrier: a single gene deletion, patients have microcytosis but no
anemia, asymptomatic
• α-Thalassemia Trait: deletion of two genes, clinically identical to βthalassemia minor: microcytosis, minimal or no anemia, and no
abnormal physical signs
• Hemoglobin H Disease: deletion of 3 genes, common in Asia, clinically
resembles β-thalassemia intermedia, HgH has very high affinity to
oxygen, leading to tissue hypoxia. It also precipitates within the RBC
which results in extravascular hemolysis
• Hydrops fetalis: deletion of 4 genes. Patients die in utero unless
transfused. Babies have severe pallor, hepatosplenomegaly and
edema. Treatment: life-long transfusion or BM transplant
Diagnosis
• Blood film: hypochromic microcytic anemia,
target cells, basophilic stippling
• Hg electrophoresis: different globin chains
have different electrical charges. Hg is
separated on gel and an electrical current is
applied. Each type of Hg migrate a specific
distance and hence can be recognized
• Basophilic stippling: aggregates of ribosomes, appear as
fine blue inclusions in RBCs
Sickle Cell Anemia
Sickle
SickleCell
CellDisease/
Disease/Anemia
Anemia
• Hereditary hemoglobinopathy that occurs
primarily in individuals of African descent
• Sickle cell disease is caused by a point
mutation in the sixth codon of β-globin that
leads to the replacement of a glutamate
residue with a valine residue
• The abnormal physiochemical properties of
the resulting sickle hemoglobin (HbS) are
responsible for the disease
• Sickle Cell Trait: heterozygosity of HgS,
carriers are largely asymptomatic, HgS ≈ 40%
• Sickle Cell Disease: homozygosity of HbS,
symptomatic, HgS ≈ 80%
• Both types of Hg are protective against
Malaria falciparum infection
Pathophysiology
• HbS molecules undergo polymerization when
deoxygenated. Initially the red cell cytosol converts from a freely
flowing liquid to a viscous gel as HbS aggregates form. With
continued deoxygenation aggregated HbS molecules assemble into
long needle-like fibers within red cells, producing a distorted sickle
shape
• This causes damage to cell membrane. Ca+2 enters the cell and
causes protein cross-linking. K+ and H2O moves out of the cell from
damaged membrane
• With repeated sickling, more damage happens until the cell shape
is irreversibly changed even if oxygenated again
• Sickle cells are fragile, leading to intravascular hemolysis
• Sickle cells are removed by macrophages, leading to extravascular
hemolysis too
Pathophysiology
• The presence of HbS underlies the major
pathologic manifestations:
(1) chronic hemolysis
(2) microvascular occlusions
(3) tissue damage
Interaction of HgS with the other types
of hemoglobin
• In heterozygotes with sickle cell trait: HgA
interferes with HbS polymerization. As a result,
red cells in heterozygous individuals do not sickle
except under conditions of profound hypoxia
• HgF inhibits the polymerization of HbS even more
than HgA; hence, infants do not become
symptomatic until they reach 5 or 6 months of
age, when the level of HgF normally falls
Mean cell hemoglobin concentration
• Higher HgS concentrations increase the probability that
aggregation and polymerization will occur during any given
period of deoxygenation. Thus, intracellular dehydration,
which increases the MCHC, facilitates sickling
• HgC is a variant of Beta chain. It tends to cause dehydration in
RBC. Thus, if it was combined with HgS (HgSC disease),
sickling takes place
• Conversely, conditions that decrease the MCHC reduce the
disease severity. This occurs when the individual is
homozygous for HbS but also has coexistent α-thalassemia,
which reduces Hb synthesis and leads to milder disease.
Intracellular PH
• A decrease in pH reduces the oxygen affinity
of hemoglobin, thereby increasing the fraction
of deoxygenated HbS at any given oxygen
tension and augmenting the tendency for
sickling
• Acidosis and hypoxia occurs in inflammation
Transit time of red cells through
microvascular beds
• Transit times in most normal microvascular
beds are too short for significant aggregation
of deoxygenated HbS to occur
• Sickling is confined to microvascular beds with
slow transit times (Spleen, BM and inflamed
tissue)
Blood morphology in sickle cell crisis
• peripheral blood demonstrates variable numbers of
irreversibly sickled cells, reticulocytosis, and target
cells, which result from red cell dehydration
• The bone marrow is hyperplastic as a result of a
compensatory erythroid hyperplasia
• Expansion of the marrow leads to bone resorption and
secondary new bone formation, resulting in prominent
cheekbones and changes in the skull that resemble a
crew-cut in x-rays
• Extramedullary hematopoiesis can also appear
• The increased breakdown of hemoglobin can cause
pigment gallstones and hyperbilirubinemia
Splenic changes
• In early childhood, the spleen is enlarged up to 500 gm by
red pulp congestion, which is caused by the trapping of
sickled red cells in the cords and sinuses
• With time, however, the chronic erythrostasis leads to
splenic infarction, fibrosis, and progressive shrinkage, so
that by adolescence or early adulthood only a small
residual splenic tissue is left; this process is
called autosplenectomy
• Howell-Jolly bodies (small nuclear remnants) are also
present in some red cells due to the asplenia
• Patients are at increased risk of bacterial infections
(Pneumococcus pneumoniae and Haemophilus
influenzae septicemia and meningitis)
Vaso-occlusive crisis
• Also called pain crises, are episodes of hypoxic injury and infarction
that cause severe pain in the affected region
• Although infection, dehydration, and acidosis (all of which favor
sickling) can act as triggers, in most instances no predisposing cause
is identified
• The most commonly involved sites are the bones, lungs, liver, brain,
spleen, penis (priapism), skin (leg ulcers), pulmonary vessels (cor
pulmonale)
• In children, painful bone crises are extremely common and often
difficult to distinguish from acute osteomyelitis. These frequently
manifest as the hand-foot syndrome or dactylitis of the bones of
the hands or feet, or both (growth retardation)
• Acute chest syndrome is a particularly dangerous type of vasoocclusive crisis involving the lungs, which typically presents with
fever, cough, chest pain, and pulmonary infiltrates
Sequestration crises
• Occurs in children with intact spleens
• Massive entrapment of sickle red cells leads to
rapid splenic enlargement, hypovolemia, and
sometimes shock
• These complications may be fatal in several
cases
• Survival from sequestration crises and the
acute chest syndrome requires treatment
with exchange transfusions.
Aplastic crises
• Acute event
• Infection of red cell progenitors by parvovirus
B19, which causes a transient cessation of
erythropoiesis and a sudden worsening of the
anemia
Diagnosis
• Blood film
• Sickling test: application of oxygen-consuming
reagent to blood
• Hemoglobin electrophoresis is also used to
demonstrate the presence of HbS
Treatment
• Hydroxyurea: (1) an increase in red cell HbF
levels, which occurs by unknown mechanisms;
and (2) an anti-inflammatory effect, which
stems from an inhibition of white cell
production
• Blood exchange
Sickle cells and malaria
• Sickle cell trait provides protection against malaria
infection, especially for Plasmodium Falciparum
• Endemic areas of malaria overlaps geographically with
areas of sickle cell disease
• Mechanism of protection is not completely known
• Suggested explanation: organism causes oxidative stress
inside RBC, which causes hypoxia and sickling, then these
RBCs are removed from circulation by phagocytes
• The environment in infected sickle cells produces more
oxygen radicals, harming the organism itself
• Duffy antigen is the receptor for P. Vivax, this antigen is
absent in many people with sickle cell trait
• Sickle cell anemia-peripheral blood smear. A, Low magnification shows
sickle cells, anisocytosis, poikilocytosis, and target cells. B,Higher
magnification shows an irreversibly sickled cell in the center
ANEMIAS OF DIMINISHED
ERYTHROPOIESIS
ANEMIAS OF DIMINISHED
ERYTHROPOIESIS
• Anemias secondary to inadequate RBC
production
• Nutritional
• Renal failure
• Chronic inflammation
• Bone marrow failure
Iron deficiency anemia
•
•
•
•
•
•
•
•
•
The most common anemia worldwide
The total body iron is about 2 gm in women and 6 gm in men
Ideal diet constitutes 10-20 mg of iron, only 10% is absorped
Most dietary iron occurs in meat products
Iron is present in human body as functional (80%) and stored
(20%)
Functional iron is found in hemoglobin, myoglobin, catalase
and cytochromes
Stored iron is found is hemosiderin and ferritin
Free iron is highly toxic
Iron absorption occurs in the proximal duodenum
Mechanism of iron homeostasis
Absorption
• Regulated
• intestine may increase rate
of absorption by 10x
• Responsive to:
• Iron status
• Erythropoietic demand
• Hypoxia
• Inflammation (↓)
Loss
• Not regulated
• Insensible losses:
• Physiologic exfoliation
(enterocytes, keratinocytes,
endometrium), 1-2 mg/day
• Bleeding
• Reproduction
Body Iron status is
regulated mainly at the
level of absorption
Iron absorption and transport
• Dietary non-heme iron is in ferric status (Fe3+)
• Iron crosses cell membrane in ferrous status
(Fe2+)
• Reduced by cytochrome
• Oxidized by Hephaestin
• Stored in ferritin in ferric status
• Transported by transferrin in ferrous status
• Presents as ferrous in non-oxygenated heme
• Oxidized to ferrous when O2 is bound to Hg
Iron metabolism
Ferroreductases
• Include cytochromes and STEAP3 enzymes
• Converts ferrous iron to ferric
DMT1
• Divalent Metal Transporter1
• Transmembrane protein found on the
apical surface of enterocytes
• Imports ferrous iron and other metals into
enterocytes
• Synthesis is regulated by the status of
body iron stores
Hephaestin
• Transmembrane protein found on the
basolateral side of enterocytes
• Exports iron from
• Converts iron from ferrous to ferric state
and exports it from enterocytes into blood
Iron metabolism
Transferrin (TF)
• 90 kD serum glycoprotein
• 10% of non-albumin protein in
serum
• Binds 2 iron atoms in Ferric state
(Fe3+)
• Carries iron throughout the
circulation
• Delivers it to cell transferrin
receptors on erthroid precursors
• Normally, only 1/3 is saturated
with iron
• All molecules solublize iron in
aqueous environments and
minimize its reactivity
Ferritin
• Stores iron within cells
• Found mainly in RES, intracellular
• Stored in hepatocytes in the liver
(from serum TF), and in macrophages
in BM and spleen (mainly from heme
catabolism)
• Holds up to 4500 iron atoms
• Oxido-reductase reactivity
• Iron can be mobilized when needed
Hemosiderin
• Aggregates of partially degraded
ferritin
• Found normally in trace amounts in
RES
• Stained blue with Prussian stain
Hepcidin
• Synthesized in the liver
• Hepcidin level in the serum correlates
positively with the iron stores in the body
• Hepcidin inhibits Ferroportin, causing
retention of iron inside enterocytes which
shed outside the body
• Hepcidin production is increased in anemia of
chronic disease secondary to IL-6
Iron metabolism
• Normal serum iron level is 120 μg/dL in men and 100
μg/dL in women
• Serum iron level does not reflect the actual status of
total body iron
• Serum ferritin is derived from the storage pool of body
iron, hence, it correlated well with body iron
• Exception: in stress conditions, ferritin increases with
other acute phase reactants
• Recycling is a major source of iron available for
erythropoesis. Macrophages is RES engulf old RBCs,
degrade heme and the retrieved iron is either stored in
ferritin or delivered to erythroid cells
Causes of iron deficiency
• Decreased dietary intake (vegetarians)
• Impaired absorption (GI disease)
• Increased demand (pregnancy)
• Chronic blood loss (GI bleeding, menorrhagea)
People at increased risk of anemia are: infants,
elderly, teenagers, low socioeconomic class
Iron deficiency
• Iron deficiency develops insidiously
• Iron stores are depleted first, marked by a decline in
serum ferritin and the absence of stainable iron in the
bone marrow
• Then a decrease in serum iron and a rise in the serum
transferrin
• Ultimately, the capacity to synthesize hemoglobin,
myoglobin, and other iron-containing proteins is
diminished, leading to microcytic anemia, impaired
work and cognitive performance, and even reduced
immunocompetence
Clinical features
• RBCs appear as microcytic and hypochromic,
Target cells
• Low serum ferritin and iron levels, low transferrin
saturation, increased total iron-binding capacity,
and
• Response to iron therapy
• Erythropoietin levels are increased, but the
marrow response is blunted by the iron
deficiency; thus, marrow cellularity usually is only
slightly increased
• Thrombocytosis
• IDA: RBCs are smaller in size and have increased
central pallor. In severe cases, different shapes
appear (poikelocytosis)
• Target cells: due to decreased Hg amount relative to cell
size. Appear in IDA, thalassemia
Megaloblastic Anemia
• Anemia associated with impairment in DNA
synthesis in hematopoietic cells special
morphologic features (large immature
erythroid precursors)
• Two types: Vitamin B12 and folate deficiency
• Vitamin B12 and folate are coenzymes
required for synthesis of thymidine
Causes of Vit B12 deficiency
• Low intake (vegans)
• Impaired GI absorption (intrinsic factor
deficiency, malabsorption disease,
gastrectomy)
• Bacterial overgrowth, parasitic infection, fish
tapeworm infestation
Causes of folate deficiency
• Low intake (inadequate diet, infancy)
• Impaired absorption (malabsorption, chronic
alcoholism, anti-convulsants, oral
contraceptives)
• Increased loss (dialysis)
• Impaired utilization (methotrexate, Vit B12
deficiency)
Pernicious Anemia
• Abnormal autoreactive T-cell response initiates direct
gastric mucosal injury, also triggers formation of
autoantibodies
• Type 1 antibody: blocks Vit B12 from binding to intrinsic
receptors
• Type 2 antibody: blocks Vit B12-intrinsic factor complex to
its ileal receptor
• Type 3 antibody: blocks Proton pumps on parietal cells (not
specific)
• With time, anemia develops, gastric glands become
atrophic
• Neurologic symptoms develop secondary to spinal cord
demyelination
Morphology
• PB: RBCs are large and oval and no central pallor, with
anisopoikelocytosis. Reticulocytes are low. Neutrophils
are large and have hypersegmented nuclear lobes (5 or
more)
• BM: hypercellular. Megaloblastic changes in erythroid
precursors (large size and immature nucleus despite
cytoplasmic maturation)
• Granulocytic precursors and megakaryocytes are also
large with multilobation
• Increased erythropoietic level as well as impaired DNA
synthesis leads to increased apoptosis in nucleated
RBCs and hemolysis
Anemia of Chronic Disease
• Most common anemia in hospitalized people
• It is associated with a reduction in the proliferation of
erythroid progenitors and impaired iron utilization
• The chronic illnesses associated with this form of
anemia can be grouped into three categories:
• Chronic microbial infections, such as osteomyelitis,
bacterial endocarditis, and lung abscess
• Chronic immune disorders, such as rheumatoid
arthritis and regional enteritis
• Neoplasms, such as carcinomas of the lung and breast,
and Hodgkin lymphoma
Pathophysiology
• The anemia of chronic disease occurs in the setting of
persistent systemic inflammation and is associated with low
serum iron, reduced total iron-binding capacity, and
abundant stored iron in tissue macrophages
• Certain inflammatory mediators, particularly interleukin-6
(IL-6), stimulate an increase in the hepatic production of
hepcidin
• Hepcidin inhibits ferriportin function in macrophages and
reduces the transfer of iron from the storage pool to
developing erythroid precursors in the bone marrow
• Hepcidin suppresses erythropoietin production, hence,
erythroid cells proliferation is not compensating well
Pathologic findings
• The red cells can be normocytic and
normochromic, or hypochromic and microcytic,
as in anemia of iron deficiency
• There are increased storage iron in marrow
macrophages, high serum ferritin level, and
reduced total iron-binding capacity
• Only successful treatment of the underlying
condition reliably corrects the anemia
• However, some patients, particularly those with
cancer, benefit from administration of
erythropoietin.
Aplastic Anemia
• A syndrome of chronic primary hematopoietic
failure and attendant pancytopenia
• In the majority of patients autoimmune
mechanisms are suspected
• Both inherited or acquired abnormalities of
hematopoietic stem cells also occur
Causes
• Most cases of "known" etiology follow exposure to chemicals and
drugs.
• Certain drugs and agents (including many cancer chemotherapy
drugs and the organic solvent benzene) cause marrow suppression
that is dose related and reversible
• In other instances, aplastic anemia arises in an unpredictable,
idiosyncratic fashion following exposure to drugs that normally
cause little or no marrow suppression. The implicated drugs include
chloramphenicol and gold salts
• Persistent marrow aplasia can also appear after a variety of viral
infections, most commonly viral hepatitis of the non-A, non-B, nonC, non-G type, which is associated with 5% to 10% of cases
• Irradiation causes BM suppression
• In the majority of cases, no known cause can be identified
Fanconi anemia
• Inherited form of aplastic anemia
• AR, defects in a multiprotein complex that is
required for DNA repair
• Marrow hypofunction becomes evident early
in life and is often accompanied by multiple
congenital anomalies, such as hypoplasia of
the kidney and spleen and bone anomalies
Pathophysiology
• Two major etiologies have been invoked: an extrinsic, immunemediated suppression of marrow progenitors; and an intrinsic
abnormality of stem cells
• Stem cells first be antigenically altered by exposure to drugs,
infectious agents, or other unidentified environmental insults.
Activated TH1 cells produce cytokines such as interferon-γ (IFNγ)
and TNF that suppress and kill hematopoietic progenitors
• Immunosuppressive drugs such as cyclosporine produce responses
in 60% of patients
• The antigens recognized by the autoreactive T cells are not well
defined. In some instances GPI-linked proteins may be the targets,
possibly explaining the previously noted association of aplastic
anemia and PNH
Pathophysiology
• In the second group, aplastic anemia results
from cytogenetic abnormality
• Abnormally short tolemers are seen in 10% of
cases
• In minority of cases, acute leukemia
complicates aplastic anemia
• In some genetically altered stem cells, the
abnormal antigen expression activates T-cells
which kills them
Pathologic findings
• The markedly hypocellular bone marrow is largely
devoid of hematopoietic cells; often only fat cells,
fibrous stroma
• Marrow aspirates often yield little material (a
"dry tap")
• If the anemia necessitates multiple transfusions,
systemic hemosiderosis can appear
• Reticulocytopenia
• No splenomegaly
Pure Red Cell Aplasia
•
•
•
•
•
•
Only erythroid progenitors are suppressed
It may occur in association with neoplasms, particularly thymoma, drug exposures,
autoimmune disorders
A special form of red cell aplasia occurs in individuals infected with parvovirus B19,
which preferentially infects and destroys red cell progenitors.
Normal individuals clear parvovirus infections within 1 to 2 weeks; as a result, the
aplasia is transient and clinically unimportant. However, in persons with moderate
to severe hemolytic anemias, even a brief cessation of erythropoiesis results in
rapid worsening of the anemia, producing an aplastic crisis.
In those who are severely immunosuppressed (such as persons with advanced HIV
infection), an ineffective immune response sometimes permits the infection to
persist, leading to chronic red cell aplasia and a moderate to severe anemia
Blackfan-Diamond anemia: a congenital form of pure red cell aplasia than appears
in infancy
Myelophthisic anemia
• Bone marrow failure secondary to physical
occupation of the marrow spaces by a
pathologic process
• Examples: metastatic cancer, granulomatous
disease, fibrosis
Chronic Renal Failure
• Anemia tends to be roughly proportional to the
severity of the uremia
• Caused by:
• 1) diminished synthesis of erythropoietin by the
damaged kidneys, which leads to inadequate red
cell production
• 2) iron deficiency due to platelet dysfunction and
increased bleeding, which is often encountered in
uremia
• Uremia causes a change in RBC membrane shape,
known as echinocytes
Liver disease
• whether toxic, infectious, or cirrhotic is associated with
anemia attributed to decreased marrow function
• Folate and iron deficiencies caused by poor nutrition and
excessive bleeding often exacerbate anemia in this setting
• Erythroid progenitors are preferentially affected depression
of the white cell count and platelets is less common but
also occurs.
• The anemia is often slightly macrocytic due to lipid
abnormalities associated with liver failure, which cause red
cell membranes to acquire phospholipid and cholesterol as
they circulate in the peripheral blood, a characteristic
shape of acanthocytes
Hypothyroidism
• Causes decrease in cell metabolism
• Results in mild normochromic normocytic
anemia
POLYCYTHEMIA
• Erythrocytosis: increase in red cells per unit volume of
peripheral blood, usually in association with an increase in
hemoglobin concentration.
• May be absolute (defined as an increase in total red cell
mass) or relative
• Relative polycythemia results from dehydration, such as
occurs with water deprivation, prolonged vomiting,
diarrhea, or the excessive use of diuretics.
• Absolute polycythemia is described as primary when the
increased red cell mass results from an autonomous
proliferation of erythroid progenitors, and secondary when
the excessive proliferation stems from elevated levels of
erythropoietin
Absolute polycythemia
• Primary polycythemia (polycythemia vera) is a
clonal, neoplastic myeloproliferative disorder
• Secondary polycythemia occurs as an Adaptive
process (lung disease, high-altitude living,
cyanotic heart disease),
Paraneoplastic: erythropoietin-secreting tumors
(e.g., renal cell carcinoma, hepatomacellular
carcinoma, cerebellar hemangioblastoma)
or Surreptitious: endurance athletes
White blood cells disorders
Non-neoplastic
Leukopenia
• Leukopenia results most commonly from a
decrease in blood granulocytes (neutrophils)
• Lymphopenia is much less common; it is
associated with rare congenital
immunodeficiency diseases, advanced human
immunodeficiency virus (HIV) infection, and
treatment with high doses of corticosteroids
Neutropenia
• A reduction in the number of granulocytes in
blood is known as neutropenia or, when
severe, agranulocytosis
• Neutropenic persons are susceptible to
bacterial and fungal infections, which can be
fatal. The risk of infection rises sharply as the
neutrophil count falls below 500 cells/μL
Causes
Decreased production
• Part of aplastic, myelophthisic, megaloblastic
anemias
• Drugs: chemotherapy, antiepileptic,
antithyroid
• Isolated: congenital disorders (SchwachmanDiamond syndrome, Kostmann disease),
acquired (some T-cell lymphoma)
Causes
Increased destruction
• Overwhelming infection
• Cyclic neutropenia
• Splenomegaly
Clinical features
•
•
•
•
Patients are very susceptible to infections
Fever, malaise, fatigue
Infections usually begin in the oral cavity
Treatment: treat the underlying cause (stop
the offending drug), Granulocytic-Colony
Stimulating Factor
Reactive Leukocytosis
• An increase in the number of white cells in the
blood is common in a variety of inflammatory
states caused by microbial and nonmicrobial
stimuli. Leukocytoses are relatively nonspecific
and are classified according to the particular
white cell series that is affected
Neutrophilia
• Infection (bacterial)
• Burn
• Tissue necrosis (myocardial infarction)
Eosinophilia
•
•
•
•
•
Allergic reactions
Parasitic infections
Drug reactions
Rheumatologic diseases
Some malignancies (Hodgkin lymphoma)
Monocytosis
• Chronic infections
• Inflammatory bowel disease
• Rheumatologic diseases
Lymphocytosis
• Viral infections
• Tuberculosis
Reactive Lymphadenitis
• Infections and nonmicrobial inflammatory stimuli
often activate immune cells residing in lymph
nodes, which act as defensive barriers
• Any immune response against foreign antigens
can lead to lymph node enlargement
(lymphadenopathy). The infections causing
lymphadenitis are varied and numerous, and may
be acute or chronic
• In most instances the histologic appearance of
the lymph node reaction is nonspecific
Reactive Lymphadenitis
• Acute lymphadenitis: neutrophilic infiltration
• Chronic lymphadenitis:
• Follicular hyperplasia: proliferation of
germinal center B-cells resulting in enlarged
follicles, occur in HIV, Toxoplasmosis,
Rheumatologic diseases
• Paracortical (diffuse) hyperplasia: proliferation
of T-cells in the interfollicular areas, caused by
viral infection, drug reaction, post vaccination
• Reactive follicular hyperplasia: note the
enlarged follicles, variable sizes and shapes
White Blood Cells
Neoplastic disorders
NEOPLASTIC PROLIFERATIONS OF
WHITE CELLS
• Lymphoid neoplasms, which include lymphomas and plasma cell
neoplasms. In many instances tumors are composed of cells
resembling some normal stage of lymphocyte differentiation, a
feature that serves as one of the bases for their classification.
• Myeloid neoplasms arise from progenitor cells that give rise to the
formed elements of the blood: granulocytes, red cells, and
platelets. The myeloid neoplasms fall into three fairly distinct
subcategories: acute myeloid leukemias, in which immature
progenitor cells accumulate in the bone marrow; myeloproliferative
disorders, in which an inappropriate increase in the production of
formed blood elements leads to elevated blood cell counts; and
myelodysplastic syndromes, which are characteristically associated
with ineffective hematopoiesis and cytopenias
• Histiocytic neoplasms include proliferative lesions of macrophages
and dendritic cells
Lymphoid neoplasms
Lymphoma
• Many types, classified based on cell of origin (B or T), cell size and
stage of maturation
• They vary widely in their clinical presentation and behavior
• Most lymphomas arise in lymph nodes, however, they can arise
from any organ
• Some characteristically manifest as leukemias, with involvement of
the bone marrow and the peripheral blood
• Generally classified as Hodgkin and non-Hodgkin lymphomas
• Non-Hodgkin lymphomas are also generally classified as low or
high-grade lymphoma
• Plasma cell tumors usually arise within the bones and manifest as
discrete masses, causing systemic symptoms related to the
production of monoclonal immunoglobulin.
Diagnosis of lymphoma
• In lymphomas, there is proliferation of lymphocytes which
came from an original cell, thus, they are monoclonal
• There is effacement of the lymph node normal architecture
• Normal lymphocytes have specific immunophenotype based
on the degree of differentiation
• Neoplastic lymphocytes show aberrant immunophenotype
• Cytogenetic abnormality is very common and sometimes is
defining the type of lymphoma
• Lymphoma is usually associated with disturbed immune
system
Acute Lymphoblastic Leukemia/ Lymphoma
• An aggressive, high-grade type of lymphoma
• Arises from precursor lymphoid cells (lymphoblasts), B
or T
• B-ALL is the most common cancer is children, arises
from BM, affecting blood, and sometimes LNs
• T-ALL occurs mainly in male adolescents, arises from
thymus, then affecting blood, BM and other tissues
• Lymphoblasts develop mutations in transcription genes
which regulate both lymphocyte differentiation and
proliferation
Clinical features
• Abrupt, stormy onset of symptoms
• Clinical signs and symptoms related to suppressed marrow
function, including fatigue (due to anemia), fever (reflecting
infections resulting from neutropenia), and bleeding
(petechiae, ecchymoses, epistaxis, gum bleeding) secondary
to thrombocytopenia
• Bone pain and tenderness, resulting from marrow expansion
and infiltration of the subperiosteum
• Generalized lymphadenopathy, splenomegaly, and
hepatomegaly due to dissemination of the leukemic
cells. These are more pronounced in ALL than in AML
• Central nervous system manifestations, including headache,
vomiting, and nerve palsies resulting from meningeal spread
• Morphology: lymphoblasts have fine
chromatin, minimal agranular cytoplasm
Chronic Lymphocytic Leukemia/Small
Lymphocytic Lymphoma
• Low grade B-cell lymphoma
• Cells are small, round, mature looking similar to
normal lymphocytes
• Affects BM and blood (CLL), or LN (SLL)
• Bcl2 (anti-apoptotic protein) is up-regulated
• The most common leukemia in elderly
• Causes derangement in immune system
(hypogammaglobulinemia), or hemolytic anemia
• Indolent course, stays stable for years
• 10% transforms into high-grade lymphoma
• A: Low-power view
shows diffuse
effacement of nodal
architecture.
• B, At high power, a
majority of the
tumor cells have the
appearance of small,
round lymphocytes.
A "prolymphocyte,"
a larger cell with a
centrally placed
nucleolus
• CLL: leukemia cells are small in size, resemble normal
lymphocytes. Burst “smudge” cells are commonly seen
Follicular Lymphoma
•
•
•
•
Common, low-grade B-cell lymphoma
Affects elderly
Arises from germinal center B-cell
Lymphoma cells have specific translocation t(14:18), in
which Bcl2 gene on chr18 fuses with IgH gene on
chr14, causing overexpression of Bcl2
• Patients has generalized lymphadenopathy
• Lymphoma cells proliferate to form abnormal, large,
crowded follicles
• Patients have indolent course, transforms into high
grade lymphoma in 40% of cases
• A, Nodular aggregates of lymphoma cells are present throughout
• B, At high magnification, small lymphoid cells with condensed
chromatin and irregular or cleaved nuclear outlines (centrocytes)
are mixed with a population of larger cells with nucleoli
(centroblasts).
Diffuse Large B Cell Lymphoma
• most common type of lymphoma in adults,
accounting for approximately 50% of adult NHLs,
also arises in children
• Arises de novo, as a transformation from low
grade B-cell lymphoma, in the setting of chronic
immune stimulation
• High-grade lymphoma, progressive and fatal if
not treated
• 80% of patients achieve complete remission after
treatment with chemotherapy
• Tumor cells have large nuclei with open chromatin and prominent
nucleoli.
Burkitt lymphoma
•
•
•
•
High-grade B-cell lymphoma
Endemic in Africa, sporadic worldwide
High association with EBV
t(8:14), myc gene fuses with IgH gene, causing
overexpression of myc, which activates other
transcription factors and causes continuous cell
proliferation
• Lymphoma commonly arises in extranodal sites (jaw,
ileum)
• Lymphoma is rapidly growing and fatal if not treated
• The tumor cells and their nuclei are fairly uniform, giving a
monotonous appearance
• high level of mitotic activity (arrowheads) and prominent nucleoli.
• The "starry sky" pattern produced by interspersed,
lightly staining, normal macrophages
Hodgkin Lymphoma
• a group of lymphoid neoplasms that differ
from NHL in several respects
• More often localized to a single axial group of
nodes (cervical, mediastinal, para-aortic)
• Orderly spread by contiguity
• Mesenteric nodes and Waldeyer ring rarely
involved
• Extra-nodal presentation rare
Hodgkin Lymphoma
• It is characterized by the presence of neoplastic
giant cells called Reed-Sternberg cells
• RS cells constitute only a minority of tumor size,
the rest is composed of reactive lymphocytes,
histiocytes and granulocytes
• neoplastic RS cells are derived from crippled,
germinal center or post-germinal center, B cells
• Immunophenotype is very different from normal
B-cells
• EBV plays a role in the evolution of disease
Clinical features
• Common in children and young adults
• Presents as painless lymphadenopathy
• Constitutional symptoms (B-symptoms), such as
fever, night sweats, and weight loss are common
• Spread: nodal disease first, then splenic disease,
hepatic disease, and finally involvement of the
marrow and other tissues
• Radiation therapy is effective in early phases,
then chemotherapy
• Reed-Sternberg cell, with two nuclear lobes, large eosinophilic e
nucleoli, and abundant cytoplasm, surrounded by lymphocytes,
macrophages, and an eosinophil
Plasma cell myeloma
• Neoplasm of plasma cells that secrets
monoclonal Immunoglobulin (M-protein)or
part of it
• Aggressive tumor, difficult to control
• Affects elderly
• Commonly associated with renal failure,
hypercalcemia, osteosclerosis, BM failure
• Clinically known as multiple myeloma
M-protein
• unlike normal plasma cells, in which the production and
coupling of heavy and light chains are tightly
balanced, neoplastic plasma cells often synthesize excess
light or heavy chains along with complete Igs
• Occasionally only light chains or heavy chains are produced
• The most common Ig is IgG, then IgA
• The free light chains are small enough to be excreted in the
urine, where they are called Bence-Jones proteins
• M-protein causes RBCs to stick together, appearing as a
stack of coins (Rouleuax formation)
• Sometimes, light chain structures are deposited in tissues
as “amyloid”
• Normal marrow
cells are largely
replaced by
plasma cells,
including forms
with multiple
nuclei,
prominent
nucleoli, and
cytoplasmic
droplets
containing Ig
Myeloid neoplasms
Myeloid neoplasms
• Arise from hematopoietic progenitor cells,
capable of differentiation to granulocytic,
erythrocytic or megakaryocytic lineages
• These diseases primarily involve the marrow and
to a lesser degree the secondary hematopoietic
organs (the spleen, liver, and lymph nodes), and
usually present with symptoms related to altered
hematopoiesis
• 3 types: acute myeloid leukemia, myelodysplastic
syndrome, myeloproliferative neoplasm
Acute myeloid leukemia
• caused by acquired oncogenic mutations that
impede differentiation, and increases
proliferation, leading to the accumulation of
immature myeloid blasts in the marrow
• Accumulated blasts leads to marrow failure
and complications related to anemia,
thrombocytopenia, and neutropenia.
• AML occurs at all ages, but the incidence rises
throughout life
Classifications
• WHO Classification
1) AML-recurrent cytogenetic abnormality
2) AML-Myelodysplasia related changes
(complicates MDS)
3) Therapy-related myeloid neoplasm
4) AML- not otherwise specified
Older Classification (FAB)
•
•
•
•
•
•
•
•
M0: AML with minimal differentiation
M1: AML without maturation
M2: AML with maturation
M3: Acute promyelocytic leukemia
M4: Acute myelomonocytic leukemia
M5: Acute monocytic leukemia
M6: Acute erythrocytic leukemia
M7: Acute megakaryocytic leukemia
AML-recurrent cytogenetic abnormality
• AML with t(8;21); Full range of myelocytic
maturation (M2); Auer rods easily found;
abnormal cytoplasmic granules, favorable Px
• AML with inv(16); Myelocytic and monocytic
differentiation; abnormal eosinophilic
precursors with abnormal basophilic granules
(M4eos), favorable Px
• AML with t(15;17); promyelocytic proliferation
(M3), intermediate Px
Morphology
• BM shows 20% of more blasts
Myeloblasts have delicate nuclear chromatin,
two to four nucleoli, and more voluminous
cytoplasm than lymphoblasts
• Auer rods: distinctive needle-like azurophilic
granules, sometimes seen
• Blasts commonly appear in peripheral blood
•
Acute promyelocytic leukemia-bone marrow aspirate. The neoplastic
promyelocytes have abnormally coarse and numerous azurophilic granules. Other
characteristic findings include the presence of several cells with bilobed nuclei and
a cell in the center of the field that contains multiple needle-like Auer rods.
Clinical features
• Patients present shortly after developing fever,
malaise, fatigue, bleeding
• Procoagulants and fibrinolytic factors released by
leukemic cells, especially in AML with the
t(15;17), exacerbate the bleeding tendency
• Infection is common
• AML is a difficult disease to treat. About 60% of
patients achieve complete remission with
chemotherapy, but only 15% to 30% remain free
of disease for 5 years
Myelodysplastic Syndromes
• Group of clonal stem cell disorders characterized
by maturation defects that are associated with
ineffective hematopoiesis and a high risk of
transformation to AML
• The clone retains the capacity to differentiate but
does so in an ineffective and disordered fashion
• These abnormal cells stay within the bone
marrow and hence the patients have peripheral
blood cytopenias
• The hallmark of MDS is persistent peripheral
cytopenia and BM morphologic dysplasia
MDS
• MDS may be either primary (idiopathic) or
secondary to previous genotoxic drug or radiation
therapy (t-MDS)
• t-MDS usually appears from 2 to 8 years after the
genotoxic exposure
• All forms of MDS can transform to AML, but
transformation occurs with highest frequency
and most rapidly in t-MDS
• Cytogenetic analysis commonly reveals
chromosomal aberrations
Types of MDS
• 1) Refractory cytopenia with unilineage dysplasia
• 2) Refractory cytopenia with multilineage
dysplasia
There is persistant cytopenia in 1 or more lines,
accompanies by BM dysplasia in the same or
more lines (e.g anemia, with dysplaia in both
erythroid and myeloid precursors). The number
of blasts in BM is <5% of all cells
Anemia is the most common form of cytopenia,
while isolated neutropenia or thrombocytopenia
are rare
• Granulocytic dysplasia: neutrophils show
hypolobated nucleus and hypogranular cytoplasm
• Erythroid dysplasia: multinucleation, large megaloblastoid erytroid
precursor
• Megakaryocytic dysplasia: megakaryocytes become
small in size, with a monolobated nucleus
Types of MDS
• 3) Refractory anemia with ring sideroblasts
• There is persistent isolated anemia. Erythroid
precursors show a ring of iron around the
nucleus. Results from abnormal iron
accumulation in the mitochondria
• Iron stain shows a ring of iron around the nucleus of
erythroid precursors
Types of MDS
• Refractory Anemia with Excess Blasts
• Any type of MDS, with increased BM blasts
between 5-20% of all cells
• Heralds progression to AML
Myeloproliferative neoplasms
• Chronic myeloproliferative disorders are marked
by the hyperproliferation of neoplastic myeloid
progenitors that retain the capacity for terminal
differentiation
• There is a persistent increase in one or more
formed elements of the peripheral blood
• The neoplastic progenitors tend to seed
secondary hematopoietic organs (the spleen,
liver, and lymph nodes), resulting in
hepatosplenomegaly (caused by neoplastic
extramedullary hematopoiesis)
Chronic Myelogenous Leukemia
• a balanced (9;22) translocation that
moves ABL from chromosome 9 to a position
on chromosome 22 adjacent to BCR
• The new chr22 is known as Pheladelphia
chromosome
• The BCR-ABL fusion gene has a tyrosine kinase
activity, stimulating the proliferation and
prolonged survival of granulocytic and
megakaryocytic cells
morphology
• Peripheral blood shows markedly increased WBC
count, sometimes exceeding 100,000 cell/uL
• Most of the cells are neutrophils,
metamyelocytes and myelocytes
• Basophils and eosinophils are also increased
• The bone marrow is hypercellular owing to
increased numbers of granulocytic and
megakaryocytic precursors
• Spleen is enlarged with extramedullary
hematopoiesis
• Chronic myelogenous leukemia-peripheral blood smear.
Granulocytic forms at various stages of differentiation are
present.
Polycythemia Vera
• P vera is characterized by an excessive proliferation of
erythroid, granulocytic, and megakaryocytic elements
(panmyelosis), but most clinical signs and symptoms
are related to an absolute increase in red cell mass
• P vera must be distinguished from relative
polycythemia, which results from hemoconcentration
• Unlike reactive forms of absolute polycythemia, p vera
is associated with low levels of serum
erythropoietin, which is a reflection of the growth
factor-independent growth of the neoplastic clone
Pathophysiology
• Caused by a mutation in JAK2 gene, which sharply
lowers the dependence of hematopoietic cells on
growth factors for growth and survival, erythroid
precursors are more sensitive than other cells
• Marked erythrocytosis results in increased viscosity
and vascular stasis, thromboses and infarctions
• Spleen and liver are enlarged
• There is plethora and cyanosis in every tissue
• Bone marrow is hypercellular
• Disease progression occurs late, which transforms into
AML
Primary Myelofibrosis
• Brief period of granulopoiesis and
megakaryopoiesis, rapidly followed my BM
fibrosis and elemenation of hematopoietic
elements
• The fibroblast proliferation is stimulated by
platelet-derived growth factor and transforming
growth factor β released from neoplastic
megakaryocytes
• Hematopoiesis takes place in spleen and liver
• RBC’s escaping the fibotic stroma in BM are
deformed and take the shape of “tear-drops”
Morphology
• BM is initially hypercellular with increased
megakaryocytes
• Later in disease, become fibrotic and
hypocellular
• Peripheral blood shows thrombocytosis,
nucleated RBCs, immature granulocytes and
tear-drop cells
• Spleen shows marked extramedullary
hematopoiesis
• Two nucleated erythroid precursors and
several teardrop-shaped red cells are evident.
Coagulation disorders
Types
•
•
•
•
•
•
•
•
Congenital or acquired
Acquired deficiencies are most common and often involve several factors
simultaneously.
Vitamin K is required for the synthesis of prothrombin and clotting factors VII,
IX, and X, and its deficiency causes a severe coagulation defect
The liver synthesizes several coagulation factors and also removes many
activated coagulation factors from the circulation; thus, hepatic parenchymal
diseases are common causes of complex hemorrhagic diatheses
DIC also may lead to multiple concomitant factor deficiencies
Rarely, autoantibodies may cause acquired deficiencies limited to a single
factor
Hereditary deficiencies of each of the coagulation factors have been identified
Hemophilia A (a deficiency of factor VIII) and hemophilia B (Christmas disease,
a deficiency of factor IX) are X-linked traits, whereas most deficiencies are
autosomal recessive disorders
Deficiencies of Factor VIII-von
Willebrand Factor Complex
• factor VIII is an essential cofactor for factor IX, which
activates factor X in the intrinsic coagulation pathway
• Circulating factor VIII binds noncovalently to vWF
• Endothelial cells are the major source of plasma vWF,
whereas most factor VIII is synthesized in the liver
• vWF is found in the plasma (in association with factor
VIII), in platelet granules, in endothelial cells within
cytoplasmic vesicles called Weibel-Palade bodies, and
in the subendothelium, where it binds to collagen
• When endothelial cells are stripped away by trauma or
injury, subendothelial vWF is exposed and binds to
platelets, mainly through glycoprotein Ib and to a lesser
degree through glycoprotein IIb/IIIa
• The most important function of vWF is to facilitate the
adhesion of platelets to damaged blood vessel walls, a
crucial early event in the formation of a hemostatic plug
• Inadequate platelet adhesion is believed to underlie the
bleeding tendency in von Willebrand disease
• In addition to its role in platelet adhesion, vWF also
stabilizes factor VIII; thus, vWF deficiency leads to a
secondary deficiency of factor VIII.
von Willebrand Disease
•
•
•
•
•
•
•
Autosomal dominant disorder
It usually presents as spontaneous bleeding from mucous membranes, excessive bleeding from
wounds, and menorrhagia
the most common inherited bleeding disorder, usually mild disease
People with von Willebrand disease have compound defects in platelet function and coagulation,
but in most cases only the platelet defect produces clinical findings
The classic and most common variant of von Willebrand disease (type I) is an autosomal dominant
disorder in which the quantity of circulating vWF is reduced but clinically insignificant
Type II is characterized by the selective loss of high-molecular-weight multimers of vWF resulting in
functional deficiency of vWF. In type IIA, the high-molecular-weight multimers are not synthesized,
leading to a true deficiency. In type IIB, abnormal "hyperfunctional" high-molecular-weight
multimers are synthesized that are rapidly removed from the circulation
These high-molecular-weight multimers cause spontaneous platelet aggregation (a situation
reminiscent of the very-high-molecular-weight multimer aggregates seen in TTP); indeed, some
people with type IIB von Willebrand disease have mild chronic thrombocytopenia, presumably due
to platelet consumption.
Hemophilia A-Factor VIII Deficiency
• X-linked recessive disorder
• Approximately 30% of cases are caused by new mutations;
in the remainder, there is a positive family history
• Severe hemophilia A is observed in people with marked
deficiencies of factor VIII (activity levels less than 1% of
normal)
• Milder deficiencies may only become apparent when other
predisposing conditions, such as trauma, are also present
• In about 10% of patients, the factor VIII concentration is
normal by immunoassay, but the coagulant activity is low
because of a mutation in factor VIII that causes a loss of
function.
Clinical features
• In symptomatic cases there is a tendency toward easy bruising and
massive hemorrhage after trauma or operative procedures
• In addition, "spontaneous" hemorrhages frequently are encountered in
tissues that normally are subject to mechanical stress, particularly the
joints, where recurrent bleeds (hemarthroses) lead to progressive
deformities that can be crippling
• Petechiae are characteristically absent
• Typically, patients with hemophilia A have a prolonged PTT that is
corrected by mixing the patient's plasma with normal plasma
• Specific factor assays are then used to confirm the deficiency of factor VIII
• In approximately 15% of those with severe hemophilia A replacement
therapy is complicated by the development of neutralizing antibodies
against factor VIII, probably because factor VIII is seen by the immune
system as a "foreign" antigen. In these persons, the PTT fails to correct in
mixing studies
Hemophilia B-Factor IX Deficiency
• X-linked disorder that is indistinguishable
clinically from hemophilia A but much less
common
• The PTT is prolonged. The diagnosis is made
using specific assays of factor IX. It is treated
by infusion of recombinant factor IX.
DISSEMINATED INTRAVASCULAR
COAGULATION
• Systemic activation of coagulation and results in the
formation of thrombi throughout the microcirculation
• As a consequence, platelets and coagulation factors are
consumed and, secondarily, fibrinolysis is activated
• Thus, DIC can give rise to either tissue hypoxia and
microinfarcts caused by myriad microthrombi or to a
bleeding disorder related to pathologic activation of
fibrinolysis and the depletion of the elements required
for hemostasis (hence the term consumptive
coagulopathy)
Pathophysiology
• Clotting is initiated by either the extrinsic pathway,
which is triggered by the release of tissue factor (tissue
thromboplastin); or the intrinsic pathway, which
involves the activation of factor XII by surface contact,
collagen, or other negatively charged substances
• Both pathways lead to the generation of thrombin
Clotting normally is limited by the rapid clearance of
activated clotting factors by the macrophages and the
liver, endogenous anticoagulants (e.g., protein C), and
the concomitant activation of fibrinolysis
Pathophysiology
• DIC usually is triggered by either (1) the release of tissue factor or
thromboplastic substances into the circulation or (2) widespread
endothelial cell damage
• Thromboplastic substances can be released into the circulation
from a variety of sources-for example, the placenta in obstetric
complications or certain types of cancer cells, particularly those of
acute promyelocytic leukemia and adenocarcinomas
• In gram-negative and gram-positive sepsis (important causes of
DIC), endotoxins or exotoxins stimulate the release of tissue factor
from monocytes
• The net result of these alterations is the enhanced generation of
thrombin and the blunting of inhibitory pathways that limit
coagulation
Pathophysiology
• Severe endothelial cell injury can initiate DIC by causing the release of
tissue factor and by exposing subendothelial collagen and von Willebrand
factor (vWF)
• Widespread endothelial injury can be produced by the deposition of
antigen-antibody complexes (e.g., in systemic lupus erythematosus), by
temperature extremes (e.g., after heat stroke or burn injury), or by
infections (e.g., due to meningococci or rickettsiae)
• DIC is most often associated with sepsis, obstetric complications,
malignancy, and major trauma (especially trauma to the brain)
• The initiating events in these conditions are multiple and complex. For
example, in obstetric conditions, tissue factor derived from the placenta,
retained dead fetus, or amniotic fluid enters the circulation; however,
shock, hypoxia, and acidosis often coexist and can lead to widespread
endothelial injury
• Trauma to the brain releases fat and phospholipids, which act as contact
factors and thereby activate the intrinsic pathway
Pathophysiology
• Whatever the pathogenetic mechanism, DIC has two consequences.
First, there is widespread fibrin deposition within the
microcirculation, causing obstruction and ischemia
• Red cells are traumatized while passing through vessels narrowed
by fibrin thrombi (microangiopathic hemolytic anemia)
• Second, a bleeding diathesis results from the depletion of platelets
and clotting factors and the secondary release of plasminogen
activators
• Plasmin cleaves not only fibrin (fibrinolysis) but also factors V and
VIII, thereby reducing their concentration further
• In addition, fibrinolysis creates fibrin degradation products. These
inhibit platelet aggregation, have antithrombin activity, and impair
fibrin polymerization, all of which contribute to the hemostatic
failure
Morphology
• In DIC microthrombi are most often found in the arterioles
and capillaries of the kidneys, adrenals, brain, and heart,
but no organ is spared
• The glomeruli contain small fibrin thrombi. These may be
associated with only a subtle, reactive swelling of the
endothelial cells or varying degrees of focal glomerulitis
• The microvascular occlusions give rise to small infarcts in
the renal cortex. In severe cases the ischemia can destroy
the entire cortex and cause bilateral renal cortical necrosis
• Microinfarcts also are commonly encountered in the brain
and are often surrounded by microscopic or gross foci of
hemorrhage. These can give rise to bizarre neurologic signs
Clinical features
•
•
•
•
•
•
•
•
•
As might be imagined, depending on the balance between clotting and bleeding tendencies,
the range of possible clinical manifestations is enormous
In general, acute DIC (e.g., that associated with obstetric complications) is dominated by a
bleeding diathesis, whereas chronic DIC (e.g., as occurs in those with cancer) tends to
manifest with signs and symptoms related to thrombosis
The abnormal clotting usually is confined to the microcirculation, but large vessels are
involved on occasion
The manifestations may be minimal, or there may be shock, with acute renal failure, dyspnea,
cyanosis, convulsions, and coma
Most often, attention is called to the presence of DIC by prolonged and copious postpartum
bleeding or by the presence of petechiae and ecchymoses on the skin
Laboratory evaluation reveals thrombocytopenia and prolongation of the PT and the PTT
Fibrin split products are increased in the plasma
The prognosis varies widely depending on the nature of the underlying disorder and the
severity of the intravascular clotting and fibrinolysis
Acute DIC can be life-threatening and must be treated aggressively fresh frozen plasma.
Conversely, chronic DIC is sometimes identified unexpectedly by laboratory testing. In either
circumstance, definitive treatment must be directed at the underlying cause.
THROMBOCYTOPENIA
• Isolated thrombocytopenia is associated with a bleeding tendency
and normal coagulation tests
• A count less than 150,000 platelets/μL generally is considered to
constitute thrombocytopenia. However, only when platelet counts
fall to 20,000 to 50,000 platelets/μL is there an increased risk of
post-traumatic bleeding
• Most bleeding occurs from small, superficial blood vessels and
produces petechiae or large ecchymoses in the skin, the mucous
membranes of the gastrointestinal and urinary tracts, and other
sites. Larger hemorrhages into the central nervous system are a
major hazard in those with markedly depressed platelet counts
• Results from either decreased production or increased
consumption/destruction
Immune Thrombocytopenic Purpura
•
•
•
•
•
•
•
Immune thrombocytopenic purpura (ITP) has two clinical subtypes. Chronic ITP is a
relatively common disorder that tends to affect women between the ages of 20 and 40
years. Acute ITP is a self-limited form seen mostly in children after viral infections
Antibodies directed against platelet membrane glycoproteins IIb/IIIa or Ib/IX complexes
can be detected in roughly 80% of cases of chronic ITP
The spleen is an important site of antiplatelet antibody production and the major site of
destruction of the IgG-coated platelets
Although splenomegaly is not a feature of uncomplicated chronic ITP, the importance of
the spleen in the premature destruction of platelets is proved by the benefits of
splenectomy, which normalizes the platelet count and induces a complete remission in
more than two thirds of patients
The bone marrow usually contains increased numbers of megakaryocytes, a finding
common to all forms of thrombocytopenia caused by accelerated platelet destruction
The onset of chronic ITP is insidious. Common findings include petechiae, easy bruising,
epistaxis, gum bleeding, and hemorrhages after minor trauma. Fortunately, more
serious intracerebral or subarachnoid hemorrhages are uncommon
The diagnosis rests on the clinical features, the presence of thrombocytopenia,
examination of the marrow, and the exclusion of secondary ITP
Thrombotic Thrombocytopenic Purpura
• TTP is associated with the pentad of fever, thrombocytopenia,
microangiopathic hemolytic anemia, transient neurologic
deficits, and renal failure
• A similar disease, Hemolytic Uremic Syndrome, has similar
manifestations but is distinguished from TTP by the absence
of neurologic symptoms, the dominance of acute renal failure,
and frequent occurrence in children after infection with E.Coli
• In both, there is a widespread formation of platelet-rich
thrombi in the microcirculation. The consumption of platelets
leads to thrombocytopenia, and the narrowing of blood
vessels by the platelet-rich thrombi results in a
microangiopathic hemolytic anemia
Pathophysiology
• Deficiency in ADAMTS 13, a metalloprotease enzyme that
degrades very-high-molecular-weight multimers of von
Willebrand factor (vWF)
• Abnormal large vWF multimers accumulate in plasma
• Under some circumstances, these giant vWF multimers promote
the formation of platelet microaggregates throughout the
circulation
• The superimposition of an endothelial cell injury (caused by
some other condition) can further promote microaggregate
formation, thus initiating or exacerbating clinically evident TTP
• ADAMTS 13 deficiency can be inherited or acquired, the latter by
way of autoantibodies that bind and inhibit the metalloprotease
Pathophysiology
• Although DIC, TTP and HUS share features such as
microvascular occlusion and microangiopathic
hemolytic anemia, they are pathogenically distinct
• Unlike in DIC, in TTP and HUS activation of the
coagulation cascade is not of primary importance, so
results of laboratory tests of coagulation (such as the
PT and the PTT) usually are normal
• TTP must be considered in any patient with
unexplained thrombocytopenia and microangiopathic
hemolytic anemia, as any delay in diagnosis can be
fatal