Albinism oculocutaneous tyrosinase-positive E70.3

It is caused by mutations in the P gene(OCA2 gene). > More than 150 mutations are now known. The gene codes for the protein that plays a key role in melanin biosynthesis as a transporter protein for melanosomal proteins such as TYR and TYRP1.

The encoded "Melanosomal Transmembrane Protein" contributes to a melanosome-specific anion (chloride) current that modulates melanosomal pH for optimal tyrosinase activity required for melanogenesis and melanosome maturation.

Remark: Intracellular ion channels are essential regulators of organellar and cellular functions. A chloride-selective anion conductance mediated by OCA2, which is required for melanin production, has been identified in skin and eye melanosomes. Expression of OCA2 increases the pH of the organelle, suggesting that the chloride channel regulates melanin synthesis by modulating melanosome pH. This finding suggests that a melanosomal anion channel exists that requires OCA2 and is essential for skin and eye pigmentation (Bellono NW et al. 2014).

At birth white hair, white skin; with increasing age slight pigmentation (hair becomes blond or reddish) Often numerous ephelids, possibly melanocytic naevi. In advanced age increased rate of UV-induced malignant epithelial tumours(basal cell carcinoma, spinocellular carcinoma). Grey-blue to light brown translucent iris, ocular fundus depigmented. Moderate nystagmus and photophobia, slight visual impairment. In patients of African descent, large melanocytic nevi and lentigines are frequently found in UV-exposed skin.

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