OCA4

OCA4, or oculocutaneous albinism type 4, is a genetic form of albinism caused by pathogenic variants in the SLC45A2 gene, also known as MATP. It is one of several subtypes of oculocutaneous albinism characterized by reduced melanin production in skin, hair, and eyes.

Inheritance is autosomal recessive, meaning two pathogenic variants (one from each parent) are typically required for an affected individual. Carriers usually have normal pigmentation and no major symptoms. The condition occurs worldwide but is reported with varying frequency in different populations.

The SLC45A2 gene encodes a membrane-associated transporter involved in melanosome function. Mutations disrupt the process that controls melanin synthesis, including melanosome maturation and pH regulation within the organelle, leading to reduced melanin production and lightened pigmentation.

Clinical features commonly include hypopigmented skin and hair, light irises with iris transillumination, and pale coloration of otroscular structures. Vision-related signs are prominent and may include nystagmus, reduced visual acuity, myopia or astigmatism, and foveal hypoplasia. Photophobia can occur due to decreased iris pigment and retinal pigment epithelium changes.

Diagnosis is based on clinical presentation supported by genetic testing that identifies biallelic variants in SLC45A2. Differential diagnosis includes other forms of OCA (types 1–3) and syndromic albinisms.

Management focuses on sun protection and skin cancer prevention, regular ophthalmologic care, and the use of visual aids and refractive correction as needed. Genetic counseling is recommended for affected individuals and their families. The prognosis depends on the severity of ocular involvement and access to appropriate visual and dermatologic care.