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. 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.
Oculocutaneous albinism type I
Ocular albinism type 1
Ocular albinism
Retinoschisis
Lafora disease
Yemenite deaf-blind hypopigmentation syndrome
Danon disease
Hypohidrotic ectodermal dysplasia