Molecular genetics of oculocutaneous albinism.

Albinism is a group of genetic disorders characterized by deficient synthesis of melanin pigment. In oculocutaneous albinism (OCA) the pigment deficiency involves the skin, hair, and eyes, whereas in ocular albinism (OA) the defect involves principally the visual system. Type I (tyrosinase-deficient) OCA results from deficient catalytic activity of tyrosinase, which catalyzes at least three steps in the melanin biosynthetic pathway. Type II (tyrosinase-positive) OCA results from abnormalities of the 'P' polypeptide, which may be a melanosomal tyrosine transporter. At least some forms of OA appear to represent mild presentations of types I and II OCA. The causes of several other forms of albinism have not yet been identified. Recent application of molecular genetic techniques to the study of these disorders has led to greatly improved knowledge of their molecular pathogenesis and relationships, and paves the way to improved diagnosis, carrier detection and prenatal diagnosis, and even to eventual treatment.