GTR Home > Conditions/Phenotypes > alpha Thalassemia

Disease characteristics

Excerpted from the GeneReview: Alpha-Thalassemia
Alpha-thalassemia (α-thalassemia) has two clinically significant forms: hemoglobin Bart hydrops fetalis (Hb Bart) syndrome and hemoglobin H (HbH) disease. Hb Bart syndrome, the more severe form, is characterized by fetal onset of generalized edema, pleural and pericardial effusions, and severe hypochromic anemia, in the absence of ABO or Rh blood group incompatibility. Clinical features include: hepatosplenomegaly, extramedullary erythropoiesis, hydrocephaly, and cardiac and urogenital defects. Death usually occurs in the neonatal period. HbH disease is characterized by microcytic hypochromic hemolytic anemia, hepatosplenomegaly, mild jaundice, and sometimes thalassemia-like bone changes. Carriers of αº-thalassemia (α-thalassemia trait) show microcytosis, hypochromia, and normal percentages of HbA2 and HbF. Carriers of α+-thalassemia (α-thalassemia silent carrier) have either a silent hematologic phenotype or present with a moderate thalassemia-like hematologic picture. Homozygosity for α+-thalassemia results in an αº-thalassemia (α-thalassemia trait) hematologic phenotype.

Associated genes

Clinical features

  • Methemoglobinemia
  • Splenomegaly
  • Cognitive impairment
  • Myelodysplasia
  • Jaundice
  • Cyanosis
  • Biliary tract abnormality
  • Hydrops fetalis
  • Hemolytic anemia
  • Polycythemia
  • Hypersplenism
  • Hypochromic microcytic anemia
  • Heinz body anemia
  • Abnormality of the heme biosynthetic pathway
  • Abnormality of immune system physiology
  • Reduced alpha/beta synthesis ratio
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Go to complete MedGen record for alpha Thalassemia

Clinical resources

Practice guidelines

  • ACOG, 2007
    ACOG technical bulletin. Hemoglobinopathies in pregnancy. Number 220--February 1996 (replaces no. 185, October 1993). Committee on Technical Bulletins of the American College of Obstetricians and Gynecologists.

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