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Hypopigmented Macules of Sun Exposed Skin in Xeroderma Pigmentosum. An Electron Microscopic Study

Patients with Xeroderma Pigmentosum (XP) frequently exhibit small, white hypopigmented spots on the parts of the body not exposed to the sun. These hypopigmented spots, 1–5 mm in diameter, appear early in the life. Punch biopsies were performed for electron microscopic studies and DOPA reaction. Melanocytes were either absent or occasionally found along the basal layer of the hypopigmented area; Langerhans cells were numerous; DOPA positive cells were rare or absent. Thus a vitiligo‐like syndrome is realized. In clinically normal skin, Langerhans cells were observed within the basal layer. These findings may help explain the clinical appearance of the white macules and the fact that the absence of pigment protection on sun exposed areas exposes the skin widely to UV radiation. It seems logical to propose that apart from the genetic enzymatic defect of XP, there is a genetic melanocytic abnormality leading to conditions which increase the general sensitivity to UV radiation.