To determine whether pigment type determines differences in epidermal function, we studied stratum corneum (SC) pH, permeability barrier homeostasis, and SC integrity in three geographically disparate populations with pigment type I–II versus IV–V skin (Fitzpatrick I–VI scale). Type IV–V subjects showed: (i) lower surface pH (≈0.5 U); (ii) enhanced SC integrity (transepidermal water loss change with sequential tape strippings); and (iii) more rapid barrier recovery than type I–II subjects. Enhanced barrier function could be ascribed to increased epidermal lipid content, increased lamellar body production, and reduced acidity, leading to enhanced lipid processing. Compromised SC integrity in type I–II subjects could be ascribed to increased serine protease activity, resulting in accelerated desmoglein-1 (DSG-1)/corneodesmosome degradation. In contrast, DSG-1-positive CDs persisted in type IV–V subjects, but due to enhanced cathepsin-D activity, SC thickness did not increase. Adjustment of pH of type I–II SC to type IV–V levels improved epidermal function. Finally, dendrites from type IV–V melanocytes were more acidic than those from type I–II subjects, and they transfer more melanosomes to the SC, suggesting that melanosome secretion could contribute to the more acidic pH of type IV–V skin. These studies show marked pigment-type differences in epidermal structure and function that are pH driven.

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This review highlights melanoma trends observed among African-, Asian-, Latino- and Native-American populations. Melanoma is the most lethal form of skin cancer, accounting for about 75% of all skin cancer deaths. Generally, incidence rates increase with age, peak after age 40, and are greater in men than women. However, these trends do not reflect what is typically seen in minority ethnic groups, where incidence rates are lower. In addition, for some groups, relative disease-specific survival also is lower compared with European-Americans. Melanomas in minority populations also tend to appear in atypical locations and are of unclear etiology. To improve our understanding of the causes of melanoma arising in ethnic minority populations future research efforts are needed. In addition, the general lack of awareness of this disease entity among minority populations and the fact that certain ethnic groups tend to present with advanced disease further highlight the need for educational programs for both patients and health care professionals.