Neurocutaneous melanosis.

BACKGROUND: Neurocutaneous melanosis (NCM) is a rare phakomatosis characterized by a focal or diffuse proliferation of melanin-producing cells in both the skin and the leptomeninges. This syndrome is believed to result from an error in the morphogenesis of embryonal neuroectoderm. FEATURES: Two-thirds of patients with NCM have giant congenital melanocytic nevi, and the remaining third have numerous lesions but no giant lesions. Most patients present neurological manifestations early in life, which can be secondary to intracranial hemorrhages, to impairment of cerebrospinal fluid circulation, and to malignant transformation of the melanocytes. PROGNOSIS: The prognosis of patients with symptomatic neurocutaneous melanosis is extremely poor, even in the absence of malignancy. Chemotherapy has been ineffective in the few patients in whom it has been tried.