FC-14   THE DISTRIBUTION OF THE CYSTINE-RICH PROTEINS IN AFRICAN HAIR COMPARED TO OTHER RACES, TRICHOTHIODYSTROPHY AND TRICHORHEXIS NODOSA: AN ELECTRON MICROSCOPY STUDY

NP Khumalo*, RPR Dawber**, DJP Ferguson*** Departments of Dermatology, Groote Schuur Hospital, Capetown, South Africa* and The Churchill Hospital, Oxford**; and the Nuffield Department of Pathology, John Radcliffe Hospital, Oxford***.

Previous light and scanning electron microscope study of normal African hair confirmed intertwining of the hairs, the presence of numerous knots and partial and complete breaks in the hair shafts compared to those of Caucasian or Asian volunteers1. This raises the question of an inherent weakness of the hair shaft (a possible explanation for this apparent increased fragility in African hair) since some of these changes are also seen in disease states of deficient sulphur in hair shafts (Trichothiodystrophy). The partial breaks of hair shafts are also seen in Trichorrhexis Nodosa, a condition thought to be due to excessive physical damage from grooming. Method: The distribution of the cystine-rich proteins in the hair of ten black South African (Negroid), was compared to that of five Caucasian and five Asian volunteers plus thirty patients with trichothiodystrophy and five trichorrhexis nodosa by transmission electron microscopy (TEM). Hairs were processed for TEM by standard protocols and thin sections examined after both routine staining and silver methenamine staining to identify the distribution of the sulphur (cystine)-rich proteins. Results and Discussion: The silver staining pattern of African hair shafts was similar to that observed for Caucasians, Asians and patients with trichorrhexis nodosa.2 The cuticular cells exhibited an electron dense A layer and exocuticle and electron lucent endocuticle. This contrasts with the distribution in trichothiodystrophy where there is disruption of the cystine-rich proteins of the A-layer and exocuticle. This suggests that the structural damage to the African hair shafts is consistent with physical trauma rather than any weakness due to an abnormality in the amount or distribution of the cystine-rich proteins. This study is consistent with there being no inherent weakness in black African hair and is consistent with the similarities in the biochemical contents of hair in various race groups3. Understanding of the normal structure of African hair is important in order to minimise the over diagnosis of conditions such as trichothiodystrophy and for the development of appropriate cosmetic treatments.

References:

1. Khumalo N.P., Doe P.T., Dawber R.P.R. and Ferguson D.J.P. J Am Acad Dermatol, 2000;43:814-20

2. Leornard J.N., Gummer C.L. and Dawber R.P.R. Br J Dermatol, 1990;103:85-90 3. Dekio S and Jidoi J. J Dermatol 1988; 15:393-6