One of two major types of thalassemia, a genetically inherited disease, in which one of the two types of polypeptides making up the hemoglobin protein is defective or missing. Hemoglobin proteins are composed of four polypeptides -- two "alpha chains" and two "beta chains". In alpha thalassemia, the alpha chains are defective or missing (see also beta thalassemia). This disease mainly affects individuals of Southeast Asian, Chinese, and Filipino ancestry; in its most severe form it results in the death of the fetus or newborn. Individuals with less severe cases have varying degrees of anemia.