G6PD

1. Glucose-6-phosphate
Dehydration Deficiency

3. Objectives
• Introduction
• Definition
• Factors cause G6PD deficiencyFactors cause G6PD deficiency
• Pathophysiology (mechanism)
• Symptoms
• Lab findings

4. Hexose monophosphate pathway
• Also called pentose phosphate pathway ‘PPP’.
• About 5% of glycolysis occurs by this pathway.
• In which:

5. Introduction
• FUNCTION OF G6PD
• Regenerates NADPH, allowing regeneration of
glutathione
• Protects against oxidative stress
• Lack of G6PD leads to hemolysis during
oxidative stress- infection, medication, fava
beans
• Oxidative stress leads to Heinz body
formation, extravascular hemolysis

6. • Pentose pathway also called the
phosphogluconate pathway and the hexose
monophosphate shunt is a process that
generates NADPH and pentoses (5-carbon
sugar)
OHHHWW MAAI GAAD!!!!
PENTOSE PATHWAY?????
(Oxidised form)(Reduced form)

7. History & Definition
• It was discovered in 1950s after it was
observed that some black soldiers
receiving antimalarial drug primaquine
developed hemolytic anemia.
• It is the most common red cell
enzymopathy associated with hemolysis.
• Large no. of abnormal genes code for the

8. Definition
• X-linked disease , sesult in G6PD
Deficiency (RBCs enzym deficiency )
asymptomatic unless Oxidative stress
causes the RBC’s to break apart.
• Inherited –, Recessive

9. Genetics
• The G6PD gene is located on the X
chromosome
• Thus the deficiency state is a sex-linked trait
• Affected males inherit the abnormal gene
from their mothers who are usually carriers
(heterozygotes)

11. G6PD Deficiency

12. G6PD variants
• There are over 400 variants of the G6PD enzyme:
• G6PD A and G6PD B are the well known variants.
G6PD B: The normal G6PD enzyme.
G6PD A: found with normal enzyme activity but
differ from B by a single amino acid substitution,
resulting in a different in electrophoretic
mobility.

13. G6PD variants
G6PD A : the common one associated with
haemolysis, electrophoretically identical to A
but has only 5- 15% of the normal enzymatic
activity.
Mediterranean G6PD: electrophoretically
identical to B but its activity is often 1% less
than normal.

14. World Health Organization classifies
for G6PD genetic variants
• Class I: Severe deficiency (<10% activity) with
chronic (nonspherocytic) hemolytic anemia
• Class II: Severe deficiency (<10% activity),
with intermittent hemolysis
• Class III: Mild deficiency (10-60% activity),
hemolysis with stressors only

15. • Class IV: Non-deficient variant, no
clinical sequelae
• Class V: Increased enzyme activity, no
clinical sequelae
World Health Organization classifies
for G6PD genetic variants

16. • Individuals who have inherited one of the many G6PD mutations do not show
clinical manifestation.
• Some of patients with G6PD develop hemolytic anemia if they are exposed or
ingest any of the followings oxidizing agents:
1-1-Oxidant drugsOxidant drugs: Remember “AAA”?
AntibioticsAntibiotics : e.g. sulfamethoxazole
AntimalariasAntimalarias : e.g. primaquine
AntipyreticsAntipyretics : e.g. acetanilid
2-2- Favism:Favism:
The hemolytic effect of ingesting of fava beans is not observed in all
individuals with G6PD deficiency but all patients with favism have G6PD
deficiency
factors cause G6PD deficiency:factors cause G6PD deficiency:

17. G6PD Deficiency
• Biochemistry – summary
• G6PD
Reduces
• NADP+
• to
• NADPH
Which is
responsible for
• Glutathione
Which fights
• Free radicals
Which damage
blood cells

18. Pathophysiology
• Oxidative denaturation of hemoglobin is the
major cause of H. A in G6PD deficiency
• It is important in the conversion of glucose-6-
P to phosphogluconate
• For subsequent production of NADPH &
reduced glutathione (GSH)
• GSH protects enzymes & hemoglobin against
oxidation by reducing H2O2 & free radicals

19. Pathophysiology
• H2O2 is generated normally in small amounts
during normal red cell metabolism
• Larger amounts produced when an oxidant
drug interacts with oxyhemoglobin
• Normal red cells have sufficient G6PD
activity to maintain adequate GSH levels
• When deficient, red cells fail to produces
sufficient G6PD to detoxify peroxide

20. Pathophysiology
• Hb is then oxidized to Hi, heme is
liberated from globin & globin denatures
producing Heinz bodies
• Heinz bodies attach to membrane
sulfhydryl groups inducing cell rigidity
• At this point red cells can no longer
traverse the splenic microcirculation
• Hence lysis occurs

21. Symptoms
• Persons with this condition do not display any signs of
the disease until their red blood cells are exposed to
certain chemicals in food or medicine, or to stress.
• Symptoms are more common in men and may include:
• Dark urine
• Enlarged spleen
• Fatigue
• Pallor
• Rapid heart rate
• Shortness of breath
• Yellow skin color (jaundice)

22. G6PD Deficiency
• Malaria Treatment
– chloroquine
– atovaquone-proguanil (Malarone®)
– artemether-lumefantrine (Coartem®)
– mefloquine (Lariam®)
– quinine
– quinidine
– doxycycline (used in combination with quinine)
– clindamycin (used in combination with quinine)
– primaquine

23. Diagnosis ofDiagnosis of
G6PD Deficiency Hemolytic AnemiaG6PD Deficiency Hemolytic Anemia
1-CBC
Bite cells, blister cells, irregular small
cells, Heinz bodies, polychromasia
G-6-PD level
Bite” cells
Spleen removes portion of RBC that had Heinz
body, preventing intravascular hemolysis
• 2-Screening:
• Qualitative assessment of G6PD enzymatic activity
(UV-based test)

24. Diagnosis ofDiagnosis of
G6PD Deficiency Hemolytic AnemiaG6PD Deficiency Hemolytic Anemia
• 3-Confirmatory test:
• Quantitative measurement of G6PD
enzymatic activity
4-Molecular test:
• Detection of G6PD gene mutation

27. Special test
• Methemoglobin reduction test

28. Methemoglobin Reduction Test
• Sodium nitrite converts Hb (hemoglobin)
to Hi (methemoglobin)
• Adding methylene blue should stimulate
the pentose phosphate pathway,
reducing methemoglobin
• In G6PD Deficiency, methemoglobin
persists

29. Methemoglobin Reduction Test
• Normal blood → clear red color
• Deficient blood → brown color
• Deficient blood
Normal blood

30. Clinical Manifestations
• The patient may experience an acute
hemolytic crisis within hours of exposure to
the oxidant stress
• Hemolytic crisis is self-limited even if the
exposure continues &
• Only older cell population is rapidly destroyed
• A minority of patients are sensitive to
exposure to fava beans (favism phenomenon)

31. What is PNH?
• Paroxysmal –
sudden onset
• Nocturnal –
occuring at night
(or early in morning
upon awakeneing)
• Hemoglobinuria
Despite the name, most patients do not present this way.

32. What is PNH?
• A rare and unusual acquired hematologic disorder
characterized by
– Intravascular hemolysis
– Bone marrow failure (cytopenias)
– Thrombosis.

33. What is PNH?
• Intravascular RBCs break down result
from Complement activation due to
absence of CD55, CD59
SymptomsSymptoms
- passage of dark brown urine in the- passage of dark brown urine in the
morningmorning..

34. . PNH –laboratory features:. PNH –laboratory features:
- pancytopenia- pancytopenia
- chronic urinary iron loss- chronic urinary iron loss
- serum iron concentration decreased- serum iron concentration decreased
- hemoglobinuria- hemoglobinuria
- hemosiderinuria- hemosiderinuria
-- positive Ham’s test (acid hemolysis test)positive Ham’s test (acid hemolysis test)
- positive sugar-water test- positive sugar-water test
- specific immunophenotype of erytrocytes- specific immunophenotype of erytrocytes
(CD59, CD55)(CD59, CD55)