A morphometric and histologic study of the scalp in psoriasis. Paradoxical sebaceous gland atrophy and decreased hair shaft diameters without alopecia.

A histologic study was designed to evaluate the pilosebaceous unit of the scalp in nonpustular patch- and plaque-stage psoriasis. Punch biopsy specimens from involved and uninvolved areas of 28 patients were sectioned in a horizontal plane for qualitative and quantitative study. All samples were evaluated in a blind mode, and data were analyzed for statistical significance. There was no evidence for alopecia of any type. Sebaceous gland atrophy was a frequent concomitant in the psoriatic lesion, with probable down-sizing of the hair follicle and thinner hair shafts. Paradoxical sebaceous gland atrophy and down-sized hair follicles in psoriasis may be due to possible inhibiting effects of yet unidentified factors produced by the epidermal lesion.