Alpha-thalassemia

one of two principal protein components of adult hemoglobin

Description
The majority of adult hemoglobin contains two types of protein subunits, alpha globin and beta globin. Defects in the alpha globin chain lead to alpha thalassemia, with the general complications of thalassemia and alpha-thalassemia specific features. Alpha globin is encoded by two virtually identical genes (HBA1 and HBA2), which with two sets of equivalent chromosomes results in four functional copies of the alpha globin gene in human. Defects in one up to all four copies of the alpha globin gene lead to alpha thalassemia with increasing degrees of severity. A defect in one copy results in alpha minor (also called alpha+ thalassemia trait or alpha thalassemia trait type 2) and symptomless carrier status, defects in two copies result in mild anemia (alpha thalassemia trait type 1), defects in three copies give hemoglobin H disease with anemia and enlarged spleen, and defects in all four copies result in prenatal or neonatal death. See thalassemia, heterozygous, homozygous