Three days after receiving trimethoprim-sulfamethoxazole, a young man develops dark urine and fatigue. Smear shows red cells with a bitten edge and small dark inclusions visible with supravital staining. The inclusions are composed of:

• A Denatured hemoglobin precipitates bound to the red cell membrane ✓
• B Nuclear DNA remnants removed by the spleen
• C Aggregated immunoglobulin on the red cell surface
• D Polymerized hemoglobin S tetramers

Explanation

Heinz bodies are precipitates of oxidized, denatured hemoglobin attached to the inner red cell membrane, seen in G6PD deficiency after oxidative drug stress such as sulfonamides, primaquine, or fava beans. Splenic macrophages pluck out these inclusions, producing bite cells. Howell-Jolly bodies are DNA remnants seen after splenectomy, and polymerized HbS defines sickle disease, neither of which fits the drug-triggered episodic hemolysis described.

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.