Treatment of reticulate acropigmentation of Kitamura with azelaic acid. An immunohistochemical and electron microscopic study.

No successful therapy has been reported for reticulate acropigmentation of Kitamura, which is an autosomal dominant dermatosis. We treated a patient with 20% azelaic acid ointment. Within several weeks the pigmentation was remarkably decreased and no side effects were observed. Histologic examination revealed an increased number of dopa-positive melanocytes. These cells reacted strongly to staining with antityrosinase antibody or antityrosinase-related protein antibody. Electron microscopic findings showed many melanosomes within melanocytes, keratinocytes, and melanophages. These findings suggest that the hyperpigmentation of reticulate acropigmentation of Kitamura is the result of an excess amount of melanin production caused by activation of melanocytes in the basal layer.