Glucose-6-phosphate dehydrogenase (G6PD) deficiency leads to an impaired regeneration of reduced glutathione, an important antioxidant, which makes RBCs more susceptible to oxidative stress and can result in episodic hemolytic anemia. The condition is inherited in an X-linked recessive pattern and is the most common human enzyme deficiency worldwide. It primarily affects males of African, Asian, and Mediterranean descent. G6PD deficiency is usually asymptomatic, but a sudden surge in oxidative stress (e.g., after infection, consumption of fava beans, or various drugs) may lead to a life-threatening hemolytic crisis. Diagnostic findings include signs of intravascular hemolysis (e.g., normocytic anemia, ↑ LDH, and ↓ haptoglobin), Heinz bodies, and bite cells on blood smear. Management mainly consists of preventing hemolysis by avoiding triggers.
- G6PD deficiency is the most common human enzyme deficiency.
- Prevalence: ∼ 400 million worldwide 
- Affects primarily males of African, Mediterranean, and Asian descent 
Epidemiological data refers to the US, unless otherwise specified.
- X-linked recessive inheritance
- G6PD is the rate-limiting enzyme of the pentose phosphate pathway (also known as the hexose monophosphate shunt). This pathway yields NADPH, which is essential for converting oxidized glutathione back to its reduced form. Reduced glutathione is capable of neutralizing reactive oxygen species (ROS) and free radicals and therefore protecting RBCs from oxidative damage.
- In the absence of reduced glutathione (e.g., due to G6PD deficiency), RBCs become susceptible to oxidative stress that can damage erythrocyte membranes, resulting in intravascular and extravascular hemolysis.
Causes of increased oxidative stress are triggers of hemolytic crisis and include:
- Fava beans
- Drugs: antimalarial drugs (e.g., chloroquine, primaquine), sulfa drugs (e.g., trimethoprim-sulfamethoxazole), nitrofurantoin, isoniazid, dapsone, NSAIDs, ciprofloxacin, chloramphenicol
- Bacterial and viral infections (most common cause): Severe enzymatic deficiency can inhibit respiratory burst activity due to reduced NADPH production in phagocytes.
- Inflammation: During an inflammatory reaction free radicals are produced and can diffuse into RBCs.
- Metabolic acidosis
- Blood smear
- Signs of intravascular
- Screening test: fluorescent spot test
- Confirmatory test: quantitative G6PD enzyme analysis
Ideally, both the screening and confirmatory tests should be performed during remission.
- Avoid triggers (see “Pathophysiology” above)
- Blood transfusions should be performed only in rare, severe cases.