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This is a clinician-written, evidence-based summary aligned to the USMLE Step 2 CK Content Outline. It is intended for medical students preparing for USMLE Step 2 CK. Management reflects current ACC/AHA, USPSTF, and APA guidelines. Always cross-reference with UpToDate, institutional protocols, and clinical judgment.
The Bottom Line
- Thalassemias cause impaired globin chain production: alpha chain deletion or beta chain mutation
- MCV is often very low with a normal or high RBC count, unlike iron deficiency where RBC count is usually low
- Beta-thalassemia trait has elevated HbA2 on electrophoresis
- Alpha-thalassemia trait may have normal electrophoresis; diagnosis can require genetic testing
- Do not give iron unless iron deficiency is proven; chronic transfusion causes iron overload requiring chelation
Overview
Thalassemias are inherited disorders of hemoglobin synthesis. Alpha-thalassemia results from deletion of one or more alpha-globin genes, while beta-thalassemia results from reduced or absent beta-globin production. Ineffective erythropoiesis, hemolysis, marrow expansion, and extramedullary hematopoiesis produce the clinical spectrum from silent carrier states to transfusion-dependent anemia.
Epidemiology
Thalassemia is more common in people with Mediterranean, Middle Eastern, African, South Asian, and Southeast Asian ancestry. Carrier states are often found incidentally on CBC. Severe beta-thalassemia major presents in infancy after fetal hemoglobin declines.
Clinical Features
Symptoms
Often asymptomatic in trait; mild fatigue may occur
Severe thalassemia: failure to thrive, pallor, jaundice, poor feeding in infancy
Bone pain or facial bone changes from marrow expansion
Symptoms of iron overload: fatigue, diabetes, heart failure, liver disease in transfusion-dependent patients
Signs
Microcytosis with target cells
Hepatosplenomegaly from extramedullary hematopoiesis
Frontal bossing and maxillary hypertrophy in severe untreated disease
Gallstones from chronic hemolysis
Hydrops fetalis in alpha-thalassemia major
Investigations
First-line
CBC with RBC count and RDWVery low MCV; RBC count often normal/high in trait; RDW often normal compared with iron deficiency
Iron studiesNormal ferritin and iron studies help distinguish from iron deficiency
Peripheral smearTarget cells, microcytosis, hypochromia, basophilic stippling may be present
Second-line
Hemoglobin electrophoresis or HPLCBeta-thalassemia trait: elevated HbA2; beta-thalassemia major: absent or markedly reduced HbA with high HbF
Genetic testingUseful for alpha-thalassemia because electrophoresis may be normal in trait
Family testing and partner screeningImportant for reproductive counseling
Specialist
Iron overload monitoringFerritin trends and MRI liver/cardiac iron in transfusion-dependent disease
Endocrine and cardiac surveillanceDiabetes, hypogonadism, hypothyroidism, cardiomyopathy from iron overload
1
Trait or minor disease
- Usually no treatment required
- Avoid empiric iron unless deficiency is documented
- Provide genetic counseling and reproductive partner testing when relevant
2
Transfusion-dependent thalassemia
- Regular transfusion program to suppress ineffective erythropoiesis
- Iron chelation with deferasirox, deferoxamine, or deferiprone when transfusion iron overload develops
- Monitor for alloimmunization, infection risk, and endocrine/cardiac complications
3
Definitive and advanced therapy
- Hematopoietic stem cell transplantation can be curative in selected patients
- Gene therapy is an emerging specialist option for selected transfusion-dependent beta-thalassemia
Complications
- Iron overload: Cardiomyopathy, liver fibrosis, diabetes, hypogonadism
- Extramedullary hematopoiesis: Bone deformity, masses, spinal cord compression
- Gallstones: Chronic hemolysis increases bilirubin stones
- Hydrops fetalis: Alpha-thalassemia major with Hb Bart disease
USMLE Step 2 CK Exam Tips
- 1Microcytosis with normal ferritin and high RBC count = thalassemia trait
- 2Beta-thalassemia trait: elevated HbA2
- 3Alpha-thalassemia trait can have normal hemoglobin electrophoresis
- 4Do not give iron for thalassemia trait unless iron deficiency is proven
- 5Severe beta-thalassemia appears after 6 months when HbF declines
- 6Chronic transfusion complication = iron overload; treat with chelation
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