Is Alpha-thalassemia inherited ?
How is alpha-thalassemia inherited? The inheritance of alpha-thalassemia is complex because the condition involves two genes: HBA1 and HBA2. People have two copies of the HBA1 gene and two copies of the HBA2 gene in each cell. Each copy is called an allele. Therefore, there are 4 alleles that produce alpha-globin, the protein that results from these genes. For each of the 2 genes, one allele is inherited from a person's father, and the other is inherited from a person's mother - so each person inherits 2 alleles from each parent. The different types of alpha-thalassemia result from the loss of some or all of these alleles. If both parents are missing at least one alpha-globin allele, each of their children are at risk of having Hb Bart syndrome or hydrops fetalis, hemoglobin H (HbH) disease, or alpha-thalassemia trait. The precise risk depends on how many alleles are missing and which combination of the HBA1 and HBA2 genes is affected. In most cases: a person with 1 mutated allele is a carrier and has no signs or symptoms a person with 2 mutated alleles may have mild signs or symptoms of alpha-thalassemia (called alpha-thalassemia minor, or alpha-thalassemia trait) a person with 3 mutated alleles has moderate to severe symptoms (called HbH disease) When there are 4 mutated alleles, the condition is called alpha-thalassemia major or hydrops fetalis. In these cases, an affected fetus usually does not survive to birth, or an affected newborn does not survive long after birth.