## Distinguishing Hereditary Spherocytosis from Hereditary Elliptocytosis ### Key Morphological and Functional Differences | Feature | Hereditary Spherocytosis | Hereditary Elliptocytosis | |---------|--------------------------|---------------------------| | **RBC Shape** | Spherical, dense | Elliptical / rod-shaped | | **Osmotic Fragility** | **Increased** (fragile in hypotonic saline) | **Normal** | | **Incubated Osmotic Fragility** | Markedly increased | Normal | | **Primary Defect** | Spectrin, ankyrin, band 3, protein 4.2 | Spectrin, protein 4.1, glycophorins | | **Hemolysis Severity** | Moderate to severe | Mild (often asymptomatic) | | **Splenectomy Benefit** | Excellent response | Minimal benefit | **Key Point:** Osmotic fragility testing is the **gold standard discriminator**. Hereditary spherocytosis RBCs lyse at higher saline concentrations (increased fragility) because their spherical shape with reduced surface-area-to-volume ratio cannot accommodate water influx. Hereditary elliptocytes remain intact in the same conditions due to their elongated shape and normal osmotic tolerance. **High-Yield:** Incubated osmotic fragility (RBCs incubated at 37°C for 24 hours before testing) is **even more discriminatory** — spherocytes show marked increase in fragility, while elliptocytes remain normal. This test is rarely done in routine practice but is a classic NEET PG question stem. **Clinical Pearl:** Hereditary elliptocytosis patients are often **asymptomatic** and discovered incidentally on blood smear. Hereditary spherocytosis typically presents with jaundice, anemia, and splenomegaly requiring intervention. [cite:Robbins 10e Ch 13]
Sign up free to access AI-powered MCQ practice with detailed explanations and adaptive learning.