The molecular genetics of albinism and piebaldism

Oculocutaneous albinism (OCA) is an autosomal-recessive genetic disorder defined by hypomelanosis in the eyes, hair, and skin. Piebaldism is an autosomal-dominant congenital leukoderma associated with a white forelock. The molecular pathogeneses of these congenital pigmentary disorders have been clarified in recent years and are briefly reviewed here.

The pathologic gene mutations causing OCA and piebaldism are as follows. When a mutated tyrosinase gene produces inactive, less active, or temperature-sensitive tyrosinase, its phenotype is tyrosinase-negative (type I-A), yellow-mutant (type I-B), or temperature-sensitive (type I-TS) OCA, respectively. Mutation of the P gene encoding the tyrosine-transporting membrane protein probably occurs in tyrosinase-positive OCA (type II). A heterozygous mutation of the c-kit gene encoding mast cell-stem cell growth factor receptor induces piebaldism.

The molecular bases of several types of OCA and piebaldism have been elucidated by gene technology, and other gene mutations causing OCA or many other pigmentary disorders will be clarified in the near future.