Effects of PUVA on the epidermal melanocyte population in psoriatic patients

The effect of PUVA treatment on the epidermal melanocyte system was studied in 24 skin biopsies from four male psoriatic patients. The patients had received 40 mg 8-methoxypsoralen and a phototoxic dose of UVA (2-12 joule/cm2), twice a week. Punch biopsies were taken from unaffected and psoriatic skin in the gluteal region before, and after three and nine treatments. The epidermal melanocytes were counted in dopa incubated split-skin preparations and the mitotic index of the keratinocytes was monitored as a control of the PUVA effect. The epidermal melanocyte number was essentially normal in non-treated psoriatic patients. During the PUVA treatment the melanin production and the DOPA activity of the melanocytes increased markedly. However, there was no significant change in the number of DOPA active melanocytes, either in the unaffected or the psoriatic skin. Thus, PUVA treatment is not necessarily associated with an increase in the number of active epidermal melanocytes.