A young man develops acute intravascular hemolysis after ingestion of fava beans; which enzyme deficiency is responsible?

A young man develops acute intravascular hemolysis after ingestion of fava beans; which enzyme deficiency is responsible?

• A. Glucose-6-phosphate dehydrogenase
• B. Pyruvate kinase
• C. Hexokinase
• D. Lactase

Answer: (A)

Red blood cells rely on the hexose monophosphate shunt to generate NADPH, which is used to keep glutathione in the reduced form and protect the cell from oxidative stress. In individuals with glucose-6-phosphate dehydrogenase deficiency, this pathway is compromised, so NADPH production drops. When exposed to oxidative stress—such as oxidant compounds in fava beans—the limited glutathione system can’t neutralize the reactive oxygen species, causing hemoglobin to oxidize and form Heinz bodies. The damaged red cells are rapidly destroyed, often within the bloodstream, leading to intravascular hemolysis known as favism. This mechanism is characteristic of G6PD deficiency, whereas the other options do not specifically explain this oxidant-triggered hemolysis: pyruvate kinase deficiency causes a different pattern of hemolysis tied to ATP production and is not a classic trigger for fava bean–related episodes; hexokinase deficiency and lactase deficiency do not produce this hemolytic response.

Red blood cells rely on the hexose monophosphate shunt to generate NADPH, which is used to keep glutathione in the reduced form and protect the cell from oxidative stress. In individuals with glucose-6-phosphate dehydrogenase deficiency, this pathway is compromised, so NADPH production drops. When exposed to oxidative stress—such as oxidant compounds in fava beans—the limited glutathione system can’t neutralize the reactive oxygen species, causing hemoglobin to oxidize and form Heinz bodies. The damaged red cells are rapidly destroyed, often within the bloodstream, leading to intravascular hemolysis known as favism. This mechanism is characteristic of G6PD deficiency, whereas the other options do not specifically explain this oxidant-triggered hemolysis: pyruvate kinase deficiency causes a different pattern of hemolysis tied to ATP production and is not a classic trigger for fava bean–related episodes; hexokinase deficiency and lactase deficiency do not produce this hemolytic response.