Albinism in black South Africans
Bothwell, Janet Elizabeth
The physiology of melanin production and features of albinism are reviewed. The purpose of this study was to establish the clinical features. prevalence, nature and significance of the pigmented lesions in sixty one South African Negroid tyrosinase positive albinos. The ultrastructure of their skin and hair bulbs was examined and its correlation to their clinical features determined. Although many of the clinical features of South African tyrosinase positive and rufous albinos have previously been described, the ultrastructure of skin and hair from this group has not been documented. Pigmented lesions have previously been noted in tyrosinase positive albinos but the nature, prevalence and significance of these lesions has not been clearly defined. The albinos came from Johannesburg and its surrounding areas. sixty two normal South African Negroids were used as controls. They were eXamined for skin, hair and eye colour and the presence and distribution of naevi, lentigines. palmoplantar pigmentation and freckles. Biopsies of naevi and freckles were examined histologically. The presence of solar elastosis, solar keratoses and skin cancers was noted. The anagen bulbs of 28 tyrosinase positive albinos and 5 rufous albinos were examined in a Hitichi H-600 electron microscope. Skin biopsies of 2 tyrosinase positive and 2 rufous albinos also were examined ultrastructurally. The findings in the rufous albinos were compared to those in 5 red-haired Caucasoids. Clinically South African Negroid tyrosinase positive albinos were found to be similar to Negroid albinos elsewhere in the world. South African rufous albinos were found to most resemble rufous Nigerians rather than Papua New Guineans. Pigmented naevi were found in 80% of tyrosinase positive and 70% of normal Negroids and the mean number per person was 12 and 17 respectively. The trunk was the main site involved in both groups. Dendritic freckles were found On sun-exposed parts in 43% of the albinos. These were distinguished by their irregular, branched shape, light to dark brown colour and large size (0.5 to 3 cm). Solar keratoses occurred more frequently in aIbinos without freckles (73% versus 50%) confirming the sun-protective role of the increased albility to form pigment in this group. There was no correlation between the number of naevi and the number of keratoses. Racially determined palmoplantar pigmented macules were found in 75% of controls and in none of the albinos. On ultrastructural examination of the skin of the tyrosinase positive albinos eumelanosomes were found in stages I to II, singly in the melanocytes and sirlgly or in groups in the keratinocytes. In the hair bulbs, these melanosomes were found singly or grouped in stages I to late stage III.In the skin of rufouss albinos, eumelanosomes were found singlY in the melanocytes in. stages I to IV and singly or in groups in the kera,tinocytes in stages III and IV. In the hair bul bs only eumelanosomes in stage I to early stage III Were seen singly and in groups. In comparing our.findings in tyrosinase positive albinos to previous reports, the melanosomes in the hair bulbs were identical, but those in the skin were slightly less melanised. Our rufous albinos seem to be a distinct genetic entity since they failed to demonstrate the phaeomelanosomes previously described in rufous albinos.
A report submitted to the Faculty of Medicine,. University of the Witwatersrand, Johannesburg in fulfilment of the requirements for the degree of Master of Medicine in Dermatology.