A 7-year-old boy from Tamil Nadu presents with severe pallor, hepatosplenomegaly, and recurrent bone pain. His mother reports transfusion dependence since age 2 years. Laboratory investigations show: Hb 7.2 g/dL, MCV 62 fL, RBC count 5.8 × 10¹²/L, reticulocyte count 8%, serum ferritin 2400 ng/mL, and elevated indirect bilirubin. Peripheral blood smear shows microcytic hypochromic RBCs with target cells and nucleated RBCs. Hemoglobin electrophoresis reveals absent HbA, elevated HbF (80%), and HbA₂ 2%. What is the most likely diagnosis?

Explanation

## Diagnosis: Beta-Thalassemia Major ### Clinical Presentation **Key Point:** Beta-thalassemia major (BTM) presents in infancy or early childhood with severe hemolytic anemia requiring regular transfusions from early life. This 7-year-old boy exhibits the classic presentation: - **Transfusion dependence** since age 2 years (hallmark of BTM) - **Severe pallor and hepatosplenomegaly** (extramedullary hematopoiesis and iron overload) - **Bone pain** (marrow expansion and iron deposition) - **Recurrent infections** (functional asplenia from transfusions and iron overload) ### Laboratory Findings | Parameter | Finding | Significance | |-----------|---------|-------------| | Hb | 7.2 g/dL | Severe anemia requiring transfusion | | MCV | 62 fL | Microcytic (target Hb < 7 g/dL in BTM) | | RBC count | 5.8 × 10¹²/L | Elevated (compensatory erythropoiesis) | | Reticulocyte count | 8% | Markedly elevated (ineffective erythropoiesis) | | Serum ferritin | 2400 ng/mL | Iron overload from transfusions | | Indirect bilirubin | Elevated | Hemolysis | | Nucleated RBCs | Present | Severe marrow stress | ### Hemoglobin Electrophoresis Pattern **High-Yield:** The electrophoresis pattern is **pathognomonic** for BTM: - **Absent HbA** (0%) — complete deletion or non-function of β-globin genes - **Elevated HbF (80%)** — γ-globin chains compensate; HbF production persists - **HbA₂ 2%** — normal or slightly elevated (δ-globin chains increase slightly) This pattern reflects **homozygous or compound heterozygous β-globin mutations** with complete or near-complete loss of β-globin synthesis. ### Pathophysiology 1. **Severe β-globin deficiency** → massive accumulation of unpaired α-globin chains 2. **α-chain precipitation** → RBC membrane damage, hemolysis, and ineffective erythropoiesis 3. **Compensatory γ-globin activation** → HbF production (fetal hemoglobin escapes α-chain toxicity) 4. **Transfusion dependence** → iron overload → organ damage (heart, liver, endocrine glands) ### Clinical Pearl **Key Point:** BTM requires **regular transfusion therapy** (typically every 3–4 weeks to maintain Hb > 9 g/dL) and **iron chelation** to prevent secondary hemochromatosis. Splenectomy may be considered if transfusion requirements increase significantly. ### Differential Diagnosis Summary | Feature | BTM | BTI | Alpha-trait | Hb H | |---------|-----|-----|-------------|------| | Transfusion dependence | Yes (early) | No/rare | No | No | | HbA | Absent | Reduced | Normal | Normal | | HbF | Very high (>70%) | Elevated | Normal | Normal | | HbA₂ | Normal/↑ | ↑ | Normal | Normal | | Hb level | <7 g/dL | 7–10 g/dL | 11–13 g/dL | 9–11 g/dL | | Genotype | β⁰/β⁰ or β⁰/β⁺ | β⁺/β⁺ or β⁰/β⁺ | −−/αα or −α/αα | −−/−α | **Mnemonic: BTMF** — Beta-Thalassemia Major = **Fetal Hb Flooded** (HbF >70%), **Ferritin Fails** (iron overload), **Frequent Transfusions** (from infancy). [cite:Robbins 10e Ch 14]