Oculocutaneous albinism in an isolated Tonga community in Zimbabwe.

Oculocutaneous albinism (OCA) is a recessively inherited genetic condition prevalent throughout sub-Saharan Africa. We now describe a cluster of tyrosinase positive OCA (OCA2) cases belonging to the Tonga ethnic group living in the Zambezi valley of northern Zimbabwe. The prevalence in this region was 1 in 1000, which is four times higher than that for the country as a whole. The gene frequency for OCA2 in this population was calculated as 0.0316, with a carrier rate of 1 in 16. Molecular analysis showed that all five affected subjects from two independent families examined were found to be homozygous for an interstitial 2.7 kb deletion mutation commonly found in OCA2 subjects in Africa. An obligate carrier from another family was heterozygous for this deletion allele. Affected subjects in this isolated community suffered health, social, and economic problems.