Glucose-6-phosphate dehydrogenase deficiency

Deficiency of the enzyme glucose-6-phosphate dehydrogenase (G6PD) in red blood cells is an inherited abnormality due to mutations of the G6PD gene on the X chromosome that renders the cells vulnerable to oxidative damage. The condition is widespread in many populations living in or originating from tropical and subtropical areas of the world because it confers a selective advantage against Plasmodium falciparum malaria. Clinical features—G6PD deficiency is mostly an asymptomatic trait, but it predisposes to acute haemolytic anaemia in response to exogenous triggers, including (1) ingestion of fava beans—favism; (2) certain bacterial and viral infections; and (3) some drugs—notably some antimalarials (e.g. primaquine), some antibiotics (e.g. sulphanilamide, dapsone, nitrofurantoin), and even aspirin in high doses. Other manifestations include (1) severe neonatal jaundice; and (2) chronic nonspherocytic haemolytic anaemia—the latter is only seen with rare specific genetic variants. The acute haemolytic attack typically starts with malaise, weakness, and abdominal or lumbar pain, followed by the development of jaundice and passage of dark urine (haemoglobinuria). Most episodes resolve spontaneously. Diagnosis relies on the direct demonstration of decreased activity of G6PD in red cells: a variety of screening tests are available, with (ideally) subsequent confirmation by quantitative assay. Prevention is by avoiding exposure to triggering factors of previously screened subjects. Prompt blood transfusion is indicated in severe acute haemolytic anaemia and may be life-saving.