G6PD deficiency
G6PD deficiency
Updated: 07/14/2024
© Jun Wang, MD, PhD
General features
- Structural defect of glucose-6-phosphate dehydrogenase
- Most common enzyme deficiency in humans
- X-linked recessive
- Causing RBCs vulnerable to oxidative injury
- High prevalence in persons of African, Asian, and Mediterranean descent
- Mediterranean variant is severe
Pathogenesis
- G6PD catalyzes the oxidation of glucose-6-phosphate and the reduction of nicotinamide adenine dinucleotide phosphate (NADP+) to nicotinamide adenine dinucleotide phosphate (NADPH)
- NADPH maintains glutathione in reduced form as scavenger for dangerous oxidative metabolites
- Only source of NADPH in RBCs
- G6PD deficiency results in susceptibility to oxidative stresses, esp in RBCs
Common causes
- Infections: Leukocyte-derived oxygen free radicals
- Drugs: Antimalarial drugs, Primaquine and chloroquine; Sulfonamides; Nitrofurantoins, etc.
- Foods: Fava beans
Clinical features
- Most patients are asymptomatic
- Hemolysis occurs with exposure to oxidative stress
Laboratory findings
o Membrane-bound denatured unstable Hb
o Seen by supravital stain
- Evidences of intravascular hemolysis: schistocytes
- Evidences of extravascular hemolysis:
o RBC morphology after Heinz bodies removed by macrophages in the spleen
§ Blister cells: Submembranous blisterlike structures
§ Degmacytes: AKA “bite” cells, will be removed by the RE system
Diagnosis
- Features suggestive of G6PD deficiency
o Anemia with decreased haptoglobin
o Elevated unconjugated bilirubin
o Blister cells, bite cells, and Heinz bodies
- Laboratory tests:
o Test for the enzymatic activity of G6PD by measuring reduction of NADP to NADPH
o Molecular tests
Management
- Avoid oxidant stress triggered by fava beans, drugs, and chemicals
- Transfusion usually not needed
- Folic acid and iron potentially useful
- No proven benefit of antioxidants such as vitamin E and selenium
- Splenectomy generally not recommended
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