Transcript No Slide Title

Diseases of
Muscle:
Histopathologic
Features
David Lacomis, MD
Organization of Skeletal Muscle Including
Connective Tissue (CT) Compartments
PERIMYSIUM
•Septa
•Nerve branches
•Muscle spindles
•Fat
•Blood vessels
ENDOMYSIUM
•Muscle fibers
•Capillaries
•Small nerve fibers
EPIMYSIUM
•Loose CT
•Blood vessels
Normal H&E-Stained Frozen Cross-Section of Skeletal Muscle
Perimysial
connective tissue
Endomysial
connective tissue
Note uniform sizes, polygonal shapes, and eccentric nuclei.
Normal H&E-Stained Longitudinal Paraffin Section
 Note the banding pattern.
 Nuclei are eccentrically placed.
Normal Structures: Muscle Spindle
and Associated Nerve Fibers (Gomori trichrome)
Spindle
Nerve Twig
Neuromuscular Junctions
 Can be identified by the esterase reaction
due to the presence of acetylcholinesterase.
Neuromuscular Junction (Electron Microscopy)
presynaptic
postsynaptic
Histochemical Staining Intensity Based on Fiber Types
Type I
Type II
Type IIB
Slow twitch,
oxidative; stain
dark with
Gomori
trichrome,
NADH, SDH, and
ATPase at acidic
pH; more lipid
than type II
Fast twitch,
glycolytic; stain
dark with ATPase
at alkaline pH and
with PAS stains,
as well as
phosphorylase
Intermediate
staining intensity
with ATPase
pH4.6
NADH
SDH
ATPase
= nicotinamide adenine dinucleotide
= succinic dehydrogenase
= adenosine triphosphatase
Normal (ATPase pH 9.4)
 Type I fibers are light
 Type II fibers are dark (pattern reverses at ATPase pH 4.3)
Ultrastructure of a Sarcomere*
Actin
I band
Myosin
H band
I band
Z
M
Z
A band
 *Extends from Z-band to Z-band.
 A band includes overlap of actin and myosin.
 Note arrangement of thick and thin filaments.
Normal (Electron Microscopy)
 Dark Abands
 Light Ibands
 Z-band is
present
in the
middle of
the light
band
 Thin
filaments
are
attached
at the Zband
Classification of Myopathies
ACQUIRED
Inflammatory Myopathies
INHERITED
Dystrophies
Polymyositis (PM)
Dystrophinopathies
Dermatomyositis (DM)
Limb-Girdle
Inclusion body myositis (IBM)
Myotonic
Granulomatous myositis
Facioscapulohumeral (FSHD)
Infectious myositis
Oculopharyngeal (OPD)
Toxic
Endocrine
Distal
Congenital
Metabolic
Mitochondrial
Glycogen & lipid storage
Muscle Biopsy
 Often necessary for final diagnosis of myopathy
 Choose site based on clinical, electrodiagnostic, or
imaging features
 Avoid “end-stage” fatty muscle
 Frozen sections most useful
 Routine stains
 Histochemistry
 Immunohistochemistry
Polymyositis
(Longitudinal Paraffin-Embedded Section)
 In all myopathies, degenerating fibers stain pale initially
and then become digested by macrophages.
 Mononuclear inflammatory cell infiltrates and many
basophilic regenerating fibers (arrow)
Polymyositis
(Longitudinal Paraffin-Embedded Section-Higher Power)
 Regenerating fiber (non-specific)
 Fiber is basophilic due to presence of increased
RNA and DNA.
 Activated plump nuclei and prominent nucleoli
Polymyositis
(Longitudinal Paraffin-Embedded Section-Higher Power)
 As regeneration advances, a myotube “bridge” is formed.
Invasion of a Non-necrotic Fiber by
Inflammatory Cells
 Seen in polymyositis, inclusion body
myositis, and a few dystrophies.
Myophagocytosis
(Esterase Stain)
 Macrophages are ingesting the remnants
of a degenerating fiber. This is a nonspecific myopathic finding.
Dermatomyositis




Perifascicular atrophy & Degeneration
Perimysial nflammatory cells surround a blood vessel.
Inflammatory cells tend to be B-cells.
Vasculitis with bowel infarction and subcutaneous
calcifications sometimes occur in the childhood form.
Perifascicular Atrophy
(NADH-Reacted Section)
Membrane Attack Complex (MAC)
(Immunohistochemical Stain)
 MAC is the terminal component of the complement pathway.
 It is often deposited in capillaries in dermatomyositis.
Inclusion Body Myositis (IBM)
Invaded fiber
 Features of chronic
myopathy with
endomysial inflammation
and rimmed vacuoles are
characteristic.
Vacuole
Lymphocytic inflammation
“Rimmed vacuoles”
(Congo Red)
 IBM: Vacuoles contain amyloid.
IBM Intracytoplasmic (within Vacuoles) or
Intranuclear Filamentous Inclusions
Granulomatous Myositis
in a Patient with Sarcoidosis
Giant cell
 Granulomas tend not to cause significant
damage to adjacent myofibers.
Endocrine Disturbance Type II Fiber Atrophy
(ATPase pH9.4)
 Characteristic of most endocrine
myopathies and steroid myopathy
Inherited Polyneuropathy
Chronic Neurogenic Atrophy
 Groups of angulated atrophic fibers
 Marked variation in myofiber size
Acute Denervation
(NADH Reaction)
 Manifested by small,
darkly staining angulated
fibers.
Denervation
(Esterase Stain)
 Denervated fibers also stain
darkly with non-specific esterase.
Chronic Neurogenic Processes
(NADH Reaction)
 Target fibers noted.
 Light center surrounded by a darker rim.
 Generally only seen in type I fibers.
Chronic Neurogenic Atrophy
(ATPase Reaction)
 Fiber type grouping
Frozen Section from a Patient with
Duchenne Muscular Dystrophy
Group of basophilic regenerating fibers
 Opaque or hyaline fibers (arrows)
 Increase in endomysial connective tissue
Normal Immunohistochemical Stain for Dystrophin
(Subsarcolemmal Staining)
Duchenne Muscular Dystrophy
(Absent Staining for Dystrophin)
Becker Muscular Dystrophy
(Reduced but Present Staining)
split fiber
(non-specific chronic change)
Female Carrier of Duchenne Muscular Dystrophy
(A Mosaic Staining Pattern)
Mutations in “Limb-Girdle” and
Other Dystrophies
INHERITANCE
GENETIC
ABNORMALITY
DISORDER
X-linked
Dystrophin
Emerin
Duchenne, Becker MD
Emery-Dreifuss MD
AD
Myotilin
Lamin A/C
Caveolin – 3
PABP2
-crystallin/Desmin
Limb-Girdle MD (LGMD 1A)
LGMD 1B
LGMD 1C
Oculopharyngeal
Myofibrillar Myopathy
AR
Calpain – 3
Dysferlin
g Sarcoglycan
a Sarcoglycan
 Sarcoglycan
Δ Sarcoglycan
Telethonin
LGMD 2A
LGMD 2B
LGMD 2C
LGMD 2D
LGMD 2E
LGMD 2F
LGMD 2G
Locations of Affected Proteins
in Muscular Dystrophies
Extracellular Matrix
Laminin-2

g 
sarcoglycans
Dystroglycan
complex

Sarcolemma
Lamin A/C
(emerin)
Caveolin 3
Dysferlin
Dystrophin
nucleus
Actin
Emery-Dreifuss Muscular Dystrophy
(Gomori Trichrome-Stained Frozen Section)
Necrotic fiber
 Variation in fiber size with many hypertrophic fibers
 Increase in endomysial connective tissue
 Nonspecific so-called dystrophic changes seen in
many of the muscular dystrophies.
 Can also be seen in any chronic myopathic disorder.
 This disorder is due to loss of the protein emerin.
Myotonic Dystrophy




Chronic changes
Marked excess in internalized nuclei
Variation in fiber sizes
Nuclear clumps (not shown)
(H & E, Paraffin)
 The excess of internalized nuclei
can lead to nuclear chains.
Myotonic Dystrophy
(NADH-Reacted Section)
 Ring fibers in which myofilaments are
organized in different directions
Fascioscapulohumeral Dystrophy (FSHD)
 The majority of dystrophies do not have a
specific histopathologic appearance.
 Clinical features are also very important.
 For example, winging of the scapula is
characteristic of FSHD.
FSH Dystrophy
 Variable non-specific changes
 Range from scattered atrophy to
“dystrophic” features.
 Inflammation can be present (arrow).
Congenital Myopathies: Central Core Myopathy
(NADH)
 Central areas of absent staining in the dark type I fibers
 Mitochondria absent
Congenital Myopathies: Central Core Myopathy
(NADH)
 The core consists of disorganized myofibrils
and the area is devoid of mitochondria.
Congenital Fiber Type Disproportion
(H&E)
 Bimodal size population
Congenital Fiber Type Disproportion
(ATPase pH 4.3)
 Smaller fibers are type I
 More numerous
 Stain lightly
 Larger or normal fibers are type II
Nemaline Myopathy
 Eosinophilic inclusions present.
Nemaline Myopathy
(Gomori Trichrome)
 Eosinophilic inclusions stain darkly.
Nemaline Myopathy
(Electron Microscopy)
 Named for thread-like appearance
 Inclusions extend from Z-band to Z-band
Muscle Biopsy from an Infant
 Internalized nuclei predominant.
 Consistent with centronuclear myopathy.
 Can be seen in other disorders such as
myotonic dystrophy with congenital onset.
Muscle Biopsy from an Infant:
Centronuclear Myopathy
 Central position of the nucleus
resembling an embryonic myotube
Metabolic: Inherited –
Mitochondrial Myopathy
 Ragged red fiber present (Gomori trichrome)
 Due to proliferation of abnormal mitochondria
Mitochondrial Myopathy
(Succinic Dehydrogenase Reaction)
 SDH-rich fibers are seen with mitochondrial proliferation.
 SDH is a respiratory chain enzyme encoded by nuclear DNA.
Cytochrome Oxidase (COX) Respiratory Chain Enzyme
Normal Fibers
Many COX-Negative Fibers
 COX-negative fibers are usually seen
with mtDNA mutations.
Mitochondrial Disorders
(Electron Microscopy)
 Aggregates of mitochondria containing
paracrystalline inclusions are frequent.
 Non-specific
Mitochondrial Disorders
(Electron Microscopy)
Higher power view of paracrystalline inclusion
(Oil-Red-O Stain)
 Increased lipid storage
 Seen in carnitine deficiency states (primary or
secondary)
 Sometimes as a consequence of certain toxins
 Focal increases can be non-specific.
Lipid Storage Myopathy
(Electron Microscopy)
Glycogen Storage Myopathies
 Some glycogen storage myopathies, such as
myophosphorylase deficiency (McArdle’s
Disease), cause subsarcolemmal blebs.
 PAS-positive due to the presence of glycogen.
 Only with acid maltase deficiency is glycogen
deposited in lysomsomes.
McArdle’s Disease
(Electron Microscopy)
 Subsarcolemmal collection
of glycogen is shown.
Acid Maltase Deficiency
(Acid Phosphatase)
Vacuolar myopathy noted.
 Due to the intralysosomal
activity of this enzyme
 Prominent staining with acid
phosphatase in vacuoles
Normal Glycogen
(PAS Stain) Control
Increased Glycogen
 Acid maltase deficiency
 Increased glycogen (diffusely and in vacuoles)