Transcript Document 7738088

GLUCOSE-6-PHOSPHATE
DEHYDROGENASE
DEFICIENCY
Practical IBL
• CASE HISTORY
– A 14 years old boy was admitted to King
Abdulaziz University Hospital complaining of
headache, anorexia, nausea, and a severe
backache. He had bouts of shivering, a
temperature of 40.6C. Malaria was suspected
and confirmed by identification of the parasite in
blood smear. The patient was treated by
primaquine. Three days later the patient said
that the urine was dark, and the following day it
was almost black. He complained of weakness
and abdominal and back pain. His sclerae were
yellow. The treating doctor requested the
following laboratory investigations on admission
and 10 days later:
On
10 days
admission
later
Normal
range
Hemoglobin, g/dl
9.2
14.5
14 - 18
Red blood cells  1012/l
3.5
5
5
Reticulocytes, %
12
4
0.5 - 1.5
Bilirubin, mol/l
340
23
2 - 14
?
?
13 - 19
Red cell glucose-6phosphate dehydrogenase,
units per gram hemoglobin
• QUESTIONS
1. Determine red cell glucose-6-phosphate
dehydrogenase activity in units/gm Hb.
2. What is the cause of changes in the laboratory
findings?
3. What is your diagnosis for such a case?
4. What are the functions of glucose-6-phosphate
dehydrogenase in different tissues?
5. What are the chemical characteristics of drugs
which would be expected to bring on a
hemolytic crisis?
6. From your knowledge in vitamins how could
you treat this case?
Peroxidation of RBC membrane lipid
→↑↑ membrane fragility → Hemolysis
Met-Hb
The function G6PD in the red cell is to generate NADPH →
reduced glutathione → protect the RBCs from the oxidative
damage by H2O2
•Glucose-6-phosphate dehydrogenase
deficiency
– The disorder is X-linked and women are affected
only if homozygous for the condition.
– G6PD deficiency does not cause any symptoms
unless the patient takes one of a number of
drugs, such as the anti-malarial primaquine. The
administration of one of these grugs causes rapid
and often severe hemolysis and jaundice.
•Glucose-6-phosphate dehydrogenase
deficiency (cont..,)
– In G6PD deficiency the red cells are not
completely lacking in the enzyme; younger cells
contain some 6% of the normal amount. This is
sufficient to provide reducing power for every day
needs
– When, however, a drug such as primaquine is
given the limited reducing power is overwhelmed,
oxidation of intracellular proteins takes place and
hemolysis, particularly of the older red cells,
follows
Measurement of G6PD activity
SAMPLE:
Blood collected in heparin, citrate or EDTA, Avoid hemolysis
T1
(on admission)
1 ml
T10
(at 10 days)
1 ml
2.5 ml
2.5 ml
Hemolysate (sample)
1 ml
1 ml
Reagent 3 (substrate)
1 ml
1 ml
Reagent 1 (buffer)
Reagent 2 (coenzyme)
Mix & incubate for 10 min. at 37 0C
Read the absorbance (A) of each tube at 710 nm against water
•CALCULATION
–G6PD U/g Hb on admission (T1)
= Absorbance of T1 X 1015.9 X 1 X 1
9.2
10
(Hb) (incubation
time)
–G6PD U/g Hb at 10 days (T10)
= Absorbance of T10 X 1015.9 X 1 X 1
14.5 10
(Hb) (incubation
time)
• Normal level of G6PD = 13-19
U/g Hb
• Your result on admission =
U/g Hb
• Your result at 10 days =
U/g Hb
• Comment on your results: G6PD deficiency