Albinism, caused by a deficiency of
melanin pigment in the skin, hair, and eye (
oculocutaneous albinism [OCA]), or primarily in the eye (
ocular albinism [OA]), results from mutations in genes involved in the biosynthesis of
melanin pigment. The lack of
melanin pigment in the developing eye leads to fovea hypoplasia and abnormal routing of the optic nerves. These changes are responsible for the nystagmus,
strabismus, and reduced visual acuity common to all types of
albinism. Mutations in six genes have been reported to be responsible for different types of oculocutaneous and
ocular albinism, including the
tyrosinase gene (TYR) and OCA1 (MIM# 203100), the
OCA2 gene and
OCA2 (MIM# 203200), the
tyrosinase-related protein-1 gene (TYRP1) and OCA3 (MIM# 203290), the HPS gene and
Hermansky-Pudlak syndrome (MIM# 203300), the CHS gene (CHS1), and
Chediak-Higashi syndrome (MIM# 214500), and the X-linked
ocular albinism gene and OA1 (MIM#300500). The function of only two of the gene products is known
tyrosinase and
tyrosinase-related protein-1 both of which are
enzymes in the
melanin biosynthetic pathway. Continued mutational analysis coupled with function/structure studies should aid our understanding of the function of the remaining genes and their role in
albinism. Mutation and polymorphism data on these genes are available from the International
Albinism Center
Albinism Database web site (http://www.cbc.umn.edu/tad).