## Enzyme Deficiency in G6PD **Key Point:** G6PD deficiency is an X-linked recessive disorder characterized by deficiency of the enzyme glucose-6-phosphate dehydrogenase, which catalyzes the first step of the pentose phosphate pathway. ### Mechanism of Hemolysis G6PD is essential for generating NADPH, which maintains reduced glutathione (GSH) in red blood cells. GSH protects RBCs from oxidative stress. Without adequate G6PD activity: 1. NADPH production decreases 2. Glutathione remains in oxidized form (GSSG) 3. RBCs become susceptible to oxidative damage 4. Hemoglobin denatures → Heinz bodies form 5. RBC membrane becomes rigid → hemolysis occurs ### Clinical Triggers **High-Yield:** Common precipitants of hemolytic crises include: - Infections (bacterial, viral) - Oxidative drugs (sulfonamides, aspirin, antimalarials, nitrofurantoin) - Fava beans (hence the name "favism") - Severe exercise or stress ### Laboratory Findings | Finding | Details | |---------|----------| | Heinz bodies | Denatured hemoglobin inclusions; seen with supravital staining | | Bite cells | RBCs with "bites" taken out after splenic removal of Heinz bodies | | Reticulocytosis | Elevated during hemolytic episodes | | G6PD assay | Diagnostic test; may be falsely normal during acute hemolysis | **Clinical Pearl:** G6PD deficiency is the most common enzymatic RBC disorder worldwide, affecting ~400 million people, particularly those of African, Mediterranean, and Asian descent. **Warning:** Do not confuse G6PD deficiency with other hemolytic anemias like hereditary spherocytosis (membrane protein defect) or pyruvate kinase deficiency (glycolytic enzyme defect). 
Sign up free to access AI-powered MCQ practice with detailed explanations and adaptive learning.