Occurs when a gene, or genes, related to the alpha globin protein are missing or changed (mutated). Four genes are involved in making the alpha hemoglobin chain. You get two from each parent. If you inherit one mutated gene, you will have no signs or symptoms of thalassemia but will be a carrier of the disease and can pass it on to your children. If you inherit two mutated genes, your thalassemia signs and symptoms will be mild. If you inherit three mutated genes, your signs and symptoms will be moderate to severe. This condition is also called hemoglobin H disease. If you inherit all four mutated genes, the condition is called alpha-thalassemia major. The most severe form of alpha-thalassemia major causes stillbirth.
Occurs when similar gene defects affect production of the beta globing protein. Two genes are involved in making the beta hemoglobin chain. You get one from each parent. If you inherit one mutated gene, you’ll have mild signs and symptoms of thalassemia. If you inherit both mutated genes, your signs and symptoms will be moderate to severe. This condition is called beta-thalassemia major or Cooley’s anemia. Children born with beta-thalassemia major are normal at birth, but develop severe anemia during the first year.