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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