A 19-year-old man develops dark urine, jaundice, and abdominal pain two days after eating fava beans. Hb 7.4 g/dL, reticulocytes 9%, indirect bilirubin elevated, LDH 1100 U/L, haptoglobin undetectable. Peripheral smear shows red cells that appear to have a portion bitten out. Direct Coombs test is negative. What is the diagnosis?

• A Warm autoimmune hemolytic anemia
• B Paroxysmal nocturnal hemoglobinuria
• C Hereditary spherocytosis
• D Glucose 6 phosphate dehydrogenase deficiency ✓

Explanation

Oxidant stress from fava beans in G6PD deficiency denatures hemoglobin into Heinz bodies, which splenic macrophages pluck out, leaving bite cells and blister cells on the smear. X linked inheritance explains the young male presentation, and the negative Coombs excludes autoimmune hemolysis. Spherocytes are absent here, ruling out hereditary spherocytosis, and PNH gives chronic intravascular hemolysis unrelated to oxidant exposure. Enzyme assay should ideally be done weeks after the episode because young reticulocytes have higher enzyme levels and may mask the defect.

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.