A 22-year-old man develops sudden dark urine and jaundice two days after eating fava beans while on primaquine prophylaxis. Hb 6.4 g/dL, reticulocytes 5%, indirect bilirubin raised, LDH high, haptoglobin undetectable. Smear shows bite cells and blister cells. Direct Coombs test is negative. What is the diagnosis?

• A Hereditary spherocytosis
• B Warm autoimmune hemolytic anemia
• C Paroxysmal nocturnal hemoglobinuria
• D G6PD deficiency with acute intravascular hemolysis ✓

Explanation

Oxidant stress from fava beans or primaquine in G6PD deficiency denatures hemoglobin, producing Heinz bodies that splenic macrophages pluck out, leaving bite cells and blister cells. The episode is self-limiting because older red cells with least enzyme are destroyed first while younger cells retain sufficient activity. Hereditary spherocytosis gives uniform spherocytes without bite cells, and a negative Coombs test excludes autoimmune hemolysis.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.