Albinism in black South Africans
Date
2016-08-17
Authors
Bothwell, Janet Elizabeth
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Abstract
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.
Description
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.