favism

Favism is a form of acute hemolytic anemia triggered by ingestion of fava beans (Vicia faba) in individuals with glucose-6-phosphate dehydrogenase (G6PD) deficiency. It represents one of the best-known environmental triggers of hemolysis in people with G6PD deficiency.

The underlying mechanism involves oxidative compounds in fava beans, such as divicine and isouramil. In G6PD-deficient red blood cells, reduced NADPH production impairs glutathione regeneration, making cells susceptible to oxidative damage. This can cause Heinz bodies and fragmented red cells, leading to hemolysis.

G6PD deficiency is an X-linked recessive condition with many variants. It is especially common in populations from the Mediterranean, Middle East, Africa, and parts of Asia. Favism occurs only in those with clinically significant enzyme deficiency, and not all individuals with G6PD deficiency develop it.

Clinical features typically begin within 24 to 72 hours after fava bean ingestion and include fatigue, pallor, jaundice, dark urine, back or abdominal pain, and a rapid heart rate. Laboratory signs of hemolysis may appear, such as a falling hematocrit, elevated indirect bilirubin, increased lactate dehydrogenase, and reduced haptoglobin. A peripheral smear may show Heinz bodies and bite cells.

Diagnosis relies on clinical history of exposure plus laboratory evidence of hemolysis and confirmation of G6PD deficiency by enzyme assay or genetic testing. G6PD levels can be falsely normal during an acute episode; testing is often repeated after recovery.

Management is supportive: stop fava beans, avoid known oxidant drugs (such as certain antibiotics and antimalarials), maintain hydration, and transfuse if severe anemia is present. Prevention focuses on avoiding triggers and, where appropriate, genetic counseling.