Oculocutaneous albinism is a genetic condition marked by a deficiency of pigment in the eyes, skin, and hair. This pigment shortage in the eyes leads to light sensitivity and reduced vision. The condition is classified based on the presence or absence of the enzyme tyrosinase. In the tyrosinase-negative category, the enzyme is missing, while in the tyrosinase-positive category, although the enzyme is present, it cannot function properly to produce melanin because it cannot access pigment cells.There are several specific inherited forms of oculocutaneous albinism:- Type IA involves the complete lack of tyrosinase and melanin, resulting in severe light sensitivity and nystagmus. This type is caused by a mutation in the tyrosinase gene (TYR) on chromosome 11q.- Type IB features reduced tyrosinase activity and is sometimes referred to as yellow albinism. Children with this type appear very pale at birth and have typical eye issues, but their skin and hair eventually develop normal color and a yellow tint, respectively.- Type II, the most prevalent form, has normal tyrosinase activity. Hair darkens over time, and freckles and moles appear naturally on the skin. This type is linked to a mutation in the oculocutaneous albinism gene (OCA2) on chromosome 15q.- Type III is defined by the absence of tyrosinase, but iris pigmentation develops within the first ten years of life. It results from a mutation in the tyrosinase-related protein-1 gene (TYRP1) on chromosome 9p.- Type IV displays normal tyrosinase activity and arises from a mutation in the MATP gene on chromosome 5p, where MATP stands for membrane-associated transporter protein.Oculocutaneous albinism is also associated with other genetic disorders, such as Hermansky-Pudlak syndrome and Chediak-Higashi syndrome.
