Deletion of two out of four alpha chain gene loci results in alpha thalassemia minor. The deletions may be homozygous (two on the same chromosome) or heterozygous (one from each of two chromosomes). Alpha thalassemia minor does not produce a clinical disease but may be discovered upon routine testing.
Both the homozygous and heterozygous form are common in Southeast Asians. The homozygous form of alpha thalassemia minor has been shown in African Americans as well.