Which biochemical finding best distinguishes G6PD deficiency from other causes of hemolytic anemia in an Indian patient presenting with acute hemolysis after fava bean consumption?

## Distinguishing G6PD Deficiency from Other Hemolytic Anemias ### Key Biochemical Marker **Key Point:** G6PD deficiency is uniquely characterized by reduced red cell reduced glutathione (GSH) and the presence of Heinz bodies (denatured hemoglobin precipitates) on supravital staining with brilliant cresyl blue or new methylene blue. ### Why This Matters G6PD catalyzes the first step of the pentose phosphate pathway, converting glucose-6-phosphate to 6-phosphogluconolactone. This reaction generates NADPH, which is essential for maintaining the reduced glutathione (GSH) pool that protects red cells from oxidative stress. **High-Yield:** When oxidative stress exceeds the cell's antioxidant capacity (due to G6PD deficiency), hemoglobin denatures and precipitates as Heinz bodies. These are pathognomonic for G6PD deficiency and are NOT seen in other hemolytic anemias. ### Comparison Table: Hemolytic Anemia Patterns | Feature | G6PD Deficiency | Autoimmune HA | Hereditary Spherocytosis | Sickle Cell | | --- | --- | --- | --- | --- | | **Heinz bodies** | ✓ Present | ✗ Absent | ✗ Absent | ✗ Absent | | **GSH level** | ↓ Reduced | Normal | Normal | Normal | | **DAT (Coombs)** | Negative | Positive | Negative | Negative | | **Spherocytes** | Absent | May be present | Present | Absent | | **Reticulocyte count** | ↑ Elevated | ↑ Elevated | ↑ Elevated | ↑ Elevated | ### Clinical Pearl Heinz bodies disappear after hemolysis resolves (they are removed by the spleen), so supravital staining must be done during or immediately after an acute hemolytic episode. This is why the test is most useful in the acute phase. **Mnemonic: HEINZ = Hemoglobin Enzyme INsufficiency (G6PD) Zips up (precipitates) under stress.** ### Pentose Phosphate Pathway Connection ```mermaid flowchart TD A[Glucose-6-phosphate]:::outcome --> B[G6PD enzyme]:::action B --> C[6-Phosphogluconolactone]:::outcome C --> D[NADPH generation]:::action D --> E[Reduced glutathione GSH regeneration]:::action E --> F[Antioxidant defense against ROS]:::action G[G6PD deficiency]:::urgent --> H[↓ NADPH production]:::urgent H --> I[↓ GSH pool]:::urgent I --> J[Oxidative stress]:::urgent J --> K[Hemoglobin denaturation]:::urgent K --> L[Heinz body formation]:::outcome ``` [cite:Lehninger Principles of Biochemistry Ch 20]