The separate subdivisions are categorized by the genes that they effect. The seven types are not evenly distributed amongst ethnic groups with OCA1 being the subtype most prominent in Caucasians - "accounting for approximately 50% of cases worldwide. "Previously, diagnosis was done from observation of hypopigmentation which is obvious at birth, but this is now insufficient early on to distinguish between the seven major types of OCA.Prenatal testing has been achieved through fetal skin biopsy followed by subsequent histologic and electron microscope examination for melanin levels. Clinical findings have established that molecular genetic testing of TYR, the gene encoding tyrosinase, can distinguish between 1A and 1B because the phenotypes can be identical during the first year of life. OCA1A results in complete loss of tyrosinase enzyme activity. Individuals with 1B will experience increased pigmentation with age because they have a very low level of melanin production that can increase. The histological approach for prenatal diagnosis is useful for all families at risk for OCA1 whereas the molecular genetic test is only helpful when at least one mutation is known. Management
There is currently no treatment for this disease. The extremely hypopigmented skin that is characteristic in OCA1 particularly leads to risk of skin damage and non-melanotic skin cancers due to increased sensitivity to UV rays. In OCA1B, because there is some presence of melanin, it grows with age and pigmentation can increase; the same cannot be said for OCA1A.
OCA Type 1A is an autosomal recessive condition, meaning there is a homozygous or compound heterozygous mutation related to the TYR gene. There are many different types of albinism, differing due to the effects of various mutations. Oculocutaneous albinism type IA is the most severe type of albinism, as it is characterized by no melanin production. Other types of albinism have limited melanin production. Because type IA Albinism has no functioning copies of the gene, it is the most severe type of albinism. The mutations on this gene lead to a complete lack of tyrosinase activity as the inactive enzyme is produced. An inactive enzyme can be caused by a missense or nonsense mutation. Due to the lack of enzymes needed to catalyze the production of melanin, patients do not have melanin protecting them from the sun, resulting in sensitive eyes, skin, and other symptoms mentioned in the signs and symptoms of OCA1A. The different forms of albinism and range of severity is dependent upon the level of melanin production, which depends on the level of tyrosinase activity. Diagnosis
Because albinism is autosomal recessive, prenatal genetic screening and genetic counseling can be performed to diagnose OCA early on. When pathogenic variants are known to be present in an affected family, carrier testing can also be conducted. The level of expression can be variable depending on the pigmentation background, so phenotypically, OCA can be expressed on a spectrum. OCA is heterogenous, with OCA1 being caused by a mutation in the TYR gene.