Oculocutaneous Albinism & Cutaneous Malignant Tumors

Abstract

Albinism is a genetically inherited disorder characterized by hypo-pigmentation of the skin, hair, and eyes due to a reduced or lack of cutaneous melanin pigment production. The mode of inheritance of albinism is thought to vary, depending on the type. The oculocutaneous type is considered autosomal recessive, and the ocular variant sex-linked. Oculocutaneous albinism exists in four forms. One form involves the tyrosinase gene (OCA1), whereas the other form (OCA2) has recently been associated with alterations of the P gene on chromosome 15. There are five types of OCA; of these OCA1 and OCA2 are by far the most frequent types. OCA type 1 (OCA1) occurs with a frequency of about 1/40000 worldwide. (SCC) carcinomas and malignant melanoma (MM) — and collectively they represent the commonest cancers of humans, with intense exposures (especially in early life) and chronic exposures being linked to MM and SCC/BCC, respectively. Globally, variation in skin pigmentation (measured by the proxy of reflectance) in indigenous populations correlates strongly with levels of UVR exposure quantified by satellite measurements, which in turn correlates strongly with latitude. As most persons with severe forms of OCA are very prone to sunburn, the progenitor basal cell keratinocytes of sun-exposed skin of albinos are at great risk of undergoing sunlight-induced malignant transformation. SCCS in albinos can arise de novo or from premalignant actinic lesions such as sunlight keratosis, in which the keratinocytes have already undergone a sunlight-induced initial transformation. Sunlight regularly causes these genetic alterations that are referred to as UVR-associated ― signature mutation and these signature mutations drive the malignant transformation of sunlight-induced SCCS [36, 38]. Initially transformed keratinocytes are immunogenic and thus generate immune responses which can modulate or control tumourigenesis, but sunlight-induced immunosuppression may critically interfere with this protective mechanism.