Autosomal recessive ocular albinism associated with a functionally significant tyrosinase gene polymorphism

Autosomal recessive ocular albinism (AROA) is a disorder characterized by reduced pigmentation of the retina and iris, hypoplastic fovea, variably reduced visual acuity and nystagmus. Pigmentation of the skin and hair is normal, but is usually slightly lighter than in unaffected sibs. We analysed 12 unrelated patients with AROA, and found that two had abnormalities of the tyrosinase (TYR) gene. These two patients were each a compound heterozygote for a different pathologic mutant allele and an allele containing a ‘normal’ polymorphism, Arg402Gln, which results in a tyrosinase polypeptide with reduced thermal stability. In these patients, AROA thus appears to represent a clinically mild form of OCA1, with a fixed visual deficit resulting from low tyrosinase activity during fetal development but with normal pigmentation of the skin and hair postnatally.