beta thalassemia

b-thalassemia

Updated: 07/12/2024

© Jun Wang, MD, PhD

 

General features

  • Very heterogenous etiology
  • Autosomal recessive, usually point mutations,
  • Reduced synthesis of beta globin chains (2 genes)
  • Two categories

o   B0: absent b-globin synthesis

o   B+: reduced b-globin synthesis

  • May also be classified by clinical severity 

o   Minor: Hb >10 gm/dL, normal to slightly elevated HbA2, HbF

o   Intermedia: Hb of 7.0-10 gm/dL, slightly elevated Hb2A, 20-40% HbF

o   Major: Hb < 7.0 gm/dL, no or minimal HbA, predominately HbF

  • Diagnosed by clinical features, Hb studies

Pathogenesis

  • Decreased Hgb production
  • Excess unpaired a chains precipitate out in erythroids

o   Ineffective erythropoeisis

o   Membrane damage

  • Extravascular hemolysis: RBCs with inclusions and membrane damage removed from the circulation
  • Enlargement of liver and spleen due to:

o   Red cell destruction

o   Extramedullary hematopoiesis

o   Iron overload later in the course of disease

Clinical features

  • Failure to thrive, pallor and abdominal swelling
  • Enlargement of liver and spleen
  • Facial feature due to bone expansion by marrow hyperplasia
  • “Chipmunk facies” with frontal bossing, maxillary expansion, saddle nose and depressed cranial vault
  • “Crew-cut/hair on end appearance”: vertical striations due to extramedullary haematopoiesis
  • Osteoporosis due to endocrine disorders, iron toxicity, and erythroid proliferation
  • Risk of infections due to anemia, iron overload, splenectomy

Laboratory findings

Hb electrophoresis findings

  • High HbF, low HbA  

Management

  • No specific treatment for beta thal minor
  • Treatment for beta thal major

o   Long-term transfusion therapy

o   Erythroid maturation agents (eg, luspatercept)

o   Iron chelation

o   Splenectomy

o   Allogeneic hematopoietic transplantation

o   Gene therapies

o   Supportive measures

 

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