AN INTRAGENIC DELETION OF THE P-GENE IS THE COMMON MUTATION CAUSING TYROSINASE-POSITIVE OCULOCUTANEOUS ALBINISM IN SOUTHERN AFRICAN NEGROIDS

Tyrosinase-positive oculocutaneous albinism (OCA2), an autosomal reces sive disorder of the melanin biosynthetic pathway, is the most common recessive disorder occurring in southern African Bantu-speaking Negroi ds, with an overall prevalence of 1/3,900. The OCA2 gene, P,has been m apped to chromosome 15q11-q13, and recently alterations in the P gene have been identified in OCA2 individuals. An intragenic deletion has b een described and proposed to be of African origin because of its occu rrence in four unrelated African American OCA2 individuals and in two individuals, one from Zaire and the other from Cameroon. This study sh ows that the intragenic deletion is a common cause of OCA2 in southern African Negroids (114/146 [.78]; OCA2 chromosomes) and is associated with one common haplotype (43/55 [.78]; OCA2 chromosomes), confirming the African origin of this allele. On the basis of haplotype data, it would appear that at least seven additional, less frequent OCA2 mutati ons occur in this population.