β-Thalassemia

Key Features

β-Thalassemia minor

• Normal neonatal screening test

• Predominantly African, Mediterranean, Middle Eastern, or Asian ancestry

• Mild microcytic, hypochromic anemia

• No response to iron therapy

• Elevated level of hemoglobin A₂

β-Thalassemia intermedia

• Ancestry as above

• Microcytic, hypochromic anemia that usually becomes symptomatic after the first few years of life with hepatosplenomegaly

β-Thalassemia major

• Neonatal screening shows hemoglobin F only

• Mediterranean, Middle Eastern, or Asian ancestry

• Severe microcytic, hypochromic anemia with marked hepatosplenomegaly

Clinical Findings

• β-thalassemia minor: patients are usually asymptomatic

• β-thalassemia intermedia: time to presentation is variable

• β-thalassemia major

  • Patients are normal at birth

  • Significant anemia develops during the first year of life

  • If the disorder is not identified and treated with blood transfusions, such children grow poorly and develop massive hepatosplenomegaly and enlargement of the medullary space with thinning of the bony cortex

• Skeletal changes (due to ineffective erythropoiesis)

  • Cause characteristic facial deformities (prominent forehead and maxilla)

  • Predispose the child to pathologic fractures

Diagnosis

• β-thalassemia minor

  • Normal neonatal screening results

  • Decreased mean corpuscular volume (MCV) with or without mild anemia subsequently develops

  • Peripheral blood smear typically shows hypochromia, target cells, and sometimes basophilic stippling

  • Hemoglobin electrophoresis performed after 6–12 months of age is usually diagnostic when levels of hemoglobin A₂, hemoglobin F, or both are elevated

• β-Thalassemia major

  • Often initially suspected when hemoglobin A is absent on neonatal screening

  • Peripheral blood smear typically shows a severe hypochromic, microcytic anemia with marked anisocytosis and poikilocytosis

  • Target cells are prominent

  • Nucleated red blood cells often exceed the number of circulating white blood cells

  • Hemoglobin level usually falls to 5–6 g/dL or less

  • Reticulocyte count is elevated

Treatment

• β-Thalassemia minor requires no specific therapy

• For β-thalassemia major, two treatments are available: chronic transfusion with iron chelation and stem cell transplantation

  • Programs of blood transfusion are generally targeted to maintain a nadir hemoglobin level of 9–10 g/dL

  • Maintenance of good health requires iron chelation; small doses of supplemental ascorbic acid may enhance the efficacy of iron chelation

  • Patients who undergo splenectomy to reduce transfusion requirements, and hence iron loading, should receive pneumococcal vaccine prior to the procedure and instructed in the use of prophylactic penicillin and urgent treatment of all febrile illness after splenectomy

• Chronic transfusion therapy is infrequently indicated for individuals with β-thalassemia intermedia

• Bone marrow or umbilical cord blood transplant is an important therapeutic option for children with β-thalassemia major who have an HLA-identical sibling donor