Oculocutaneous albinism (OCA) is manifested by reduced synthesis of melanin, which may result from mutations in a variety of genes. In OCA, hypopigmentation is both cutaneous and ocular, and in the most common types of OCA, other tissues and organs are not significantly involved. Hypopigmentation of the skin is associated with psychological and social problems, decreases natural protection against sunburn, and results in predisposition to skin cancer. In the absence of melanin in the eye, development of the visual pathways is abnormal, resulting in decreased visual acuity, strabismus, nystagmus and photophobia.
One of the most common types of OCA is OCA1, an autosomal recessive disorder of reduced pigmentation in the hair, skin and eyes, resulting from mutations in the tyrosinase gene (TYR), a five exon gene spanning approximately 60 kb on chromosome 11q. Two different types of OCA1, A and B, can be distinguished in humans, based mainly on clinical observation, wherein OCA1A is the more severe type with absence of tyrosinase activity and pigmentation throughout life. The molecular basis of OCA1 is quite heterogeneous, and more than 190 mutations in the TYR gene have been identified so far in different population groups.