## Distinguishing β-Thalassemia Major from Hereditary Spherocytosis ### Hematologic and Morphologic Comparison | Feature | β-Thalassemia Major | Hereditary Spherocytosis | |---------|-------------------|------------------------| | **MCV** | **Markedly low** (60–70 fL) | Normal to slightly low | | **RBC Morphology** | Target cells, anisopoikilocytosis, nucleated RBCs | Spherocytes, polychromasia | | **Hemoglobin Pattern** | HbF elevated, HbA absent, HbA2 elevated | Normal hemoglobin pattern | | **Iron Studies** | Iron overload (secondary hemochromatosis) | Normal iron metabolism | | **DAT/Coombs** | Negative | Negative | | **Osmotic Fragility** | Normal | Increased | | **Inheritance** | Autosomal recessive | Autosomal dominant (75%) | | **Age of Onset** | Infancy (6–12 months) | Variable; often childhood | **Key Point:** The **microcytic, hypochromic** picture with **target cells** is pathognomonic for β-thalassemia major. The MCV is markedly reduced (60–70 fL) due to defective hemoglobin synthesis, whereas hereditary spherocytosis has a **normal or near-normal MCV** with spherocytic morphology. **High-Yield:** Target cells (codocytes) in thalassemia result from the combination of microcytosis and reduced hemoglobin content — the RBC appears as a "target" with a dense central core surrounded by a pale ring. This is **absent in hereditary spherocytosis**, where RBCs are dense and spherical. **Mnemonic:** **"THALASSEMIA = TARGET cells"** — The morphologic hallmark of thalassemia is target cells due to microcytosis and hypochromia. **Clinical Pearl:** Both conditions can present with hemolytic anemia, splenomegaly, and gallstones, but the **blood smear morphology and MCV** immediately distinguish them. Thalassemia major requires transfusion dependence from infancy; hereditary spherocytosis is often managed conservatively or with splenectomy. [cite:Robbins 10e Ch 13]
Sign up free to access AI-powered MCQ practice with detailed explanations and adaptive learning.