Numerous and different methods of survey have been suggested and developed in recent years, but none of them appears to be entirely satisfactory. Insufficient classification, inadequate follow-up, incongruous rotation of investigators, notable variations in attendance, racial differences of the population submitted to statistical study, and other minor factors may account for possible errors and differences in evaluating the findings. We have conducted a survey, over a 3-year period, of the incidence of skin diseases affecting our urban black population, living in the township of Soweto (800,000 inhabitants) and attending our dermatological service at Baragwanath Hospital. Although this population is made up of a dozen different ethnic groups, they are fully urbanized and live under similar conditions and according to similar customs. We believe that the statistical data derived from these patients represent a significant expression of a uniform community.
Sebum composition has been measured in 51 patients with varying degrees of pellagra and compared with a control group of subjects in the same geographic area. In the pellagra group the wax ester percentage was 14-9 versus the normal of 21-9%. The squalene percentage was increased in the pellagra group (11-6%) versus a control value of 8-4%. A small increase in the percentage of cholesterol was also noted. These changes, which previously have been observed in starved but otherwise normal subjects, were reversible with adequate refeeding.
A 41-year-old man developed squamous-cell carcinoma within a verrucous nevus of linear distribution of a long duration. Controversial cases have been reported in the literature. Such malignant change in verrucous nevus is extremely rare.
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