Which peripheral blood smear finding is characteristic of glucose-6-phosphate dehydrogenase (G6PD) deficiency during an acute hemolytic episode?

Explanation

## G6PD Deficiency: Heinz Bodies and Acute Hemolysis **Key Point:** Heinz bodies are pathognomonic intracellular inclusions seen in G6PD deficiency during acute hemolytic crises. They represent denatured, precipitated hemoglobin and are best visualized with supravital stains (brilliant cresyl blue or new methylene blue). ### Heinz Bodies: Formation and Significance | Aspect | Detail | |--------|--------| | Composition | Denatured, oxidized hemoglobin (β-globin chains) | | Staining | Supravital stains (brilliant cresyl blue, new methylene blue) | | Appearance | Small, round, dark-staining inclusions at RBC periphery | | Timing | Appear within hours of oxidative stress | | Mechanism | Oxidative damage → loss of reducing power → Hb denaturation | **High-Yield:** Heinz bodies are removed by the spleen during passage through splenic sinusoids, creating "bite cells" (RBCs with a bite-like defect). This is a hallmark finding during acute hemolysis in G6PD deficiency. ### G6PD Deficiency Pathophysiology 1. **Enzyme deficiency:** G6PD catalyzes the first step of the pentose phosphate pathway 2. **Loss of NADPH:** Reduced NADPH → inability to regenerate reduced glutathione (GSH) 3. **Oxidative stress:** Oxidizing agents (drugs, fava beans, infection) overwhelm antioxidant defenses 4. **Hemoglobin denaturation:** Oxidative damage → Heinz body formation 5. **Hemolysis:** Splenic sequestration and destruction of Heinz-body-containing RBCs **Clinical Pearl:** Heinz bodies are NOT visible on routine Wright-Giemsa staining — supravital staining is mandatory. Bite cells (RBCs with a "bite" taken out) are visible on routine smear and indicate recent Heinz body removal by the spleen. **Mnemonic:** **G6PD-HB** — **G**lucose-6-phosphate dehydrogenase deficiency → **H**einz **B**odies during oxidative stress. ### Triggers for Acute Hemolysis in G6PD Deficiency - **Drugs:** Sulfonamides, aspirin, antimalarials (primaquine), nitrofurantoin, dapsone - **Infections:** Bacterial or viral infections (fever itself is an oxidative stressor) - **Fava beans:** Divicine and isouramil (oxidizing compounds) - **Other:** Severe exercise, metabolic acidosis [cite:Robbins 10e Ch 12]