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Information for Patients

Frequently Asked Questions

Thalassemia is an inherited blood disorder in which red blood cells (RBCs) are unable to make sufficient hemoglobin, leading to decreased cell survival.

There are 2 main types of thalassemia, alpha and beta. They are named after the 2 types of proteins found in normal hemoglobin, or HbA.


Alpha-thalassemia is caused by inherited defects in the HBA1 and HBA2 genes. Disease severity is dependent on how many alleles are affected. Usually a person with:

  • 1 mutated allele is a carrier and will have no signs or symptoms
  • 2 mutated alleles has alpha-thalassemia minor, or alpha-thalassemia trait. They may have mild signs or symptoms
  • 3 mutated alleles has HbH disease. They may have moderate to severe symptoms
  • 4 mutated alleles has alpha-thalassemia major, or hydrops fetalis. This condition is fatal; fetuses typically do not survive to birth and newborns do not survive for long after birth


Mutations in the HBB gene cause beta-thalassemia. Disease severity is dependent on whether one or both inherited alleles contain mutations.

A person with:

  • 1 gene mutation has thalassemia minor, or thalassemia trait. They typically have mild symptoms. In rare cases, the gene mutation may be dominant and the person may have more severe signs and symptoms
  • 2 gene mutations may have either thalassemia intermedia or thalassemia major (also called Cooley’s anemia)
    • Thalassemia major is more severe; it typically presents prior to age 2
    • Thalassemia intermedia is less severe; it typically presents after age 2

Mitapivat is not approved by health authorities for the treatment of thalassemia.