RESUMEN
BACKGROUND AND OBJECTIVE: Atrophoderma of Pasini and Pierini (APP) is an uncommon cutaneous disorder, with no known effective treatment, manifested by hyperpigmented patches that appear to be depressed compared with surrounding skin. This study investigated the effectiveness of the Q-switched alexandrite laser on a patient with extensive APP, and evaluated histopathologic and ultrastructural changes. STUDY DESIGN/MATERIALS AND METHODS: A man with stable APP underwent Q-switched alexandrite laser treatment to a patch on the trunk. Biopsies were obtained from treated and untreated sites of involvement. Light and transmission electron microscopic evaluation was performed to investigate melanosome number, size, and volume, as well as melanin granule number and size. RESULTS: After three treatment sessions, the treated area showed marked clinical improvement. Electron microscopy showed a 19% reduction in melanin granule number and size and a 65% reduction in melanosome number, size, and volume in larger melanosomes in treated compared with untreated sites. CONCLUSION: Treatment of APP with the Q-switched alexandrite laser results in clinical improvement. Electron microscopic evaluation suggests that the mechanism may be a reduction in the number, size, and volume of larger melanosomes as well as a decrement in melanin granule number and size.