Neurocutaneous melanosis (NCM)
is a rare, non-inherited condition of the central nervous system. It is characterized by melanocytic nevi in both the skin and the brain. Two-thirds of people with NCM have giant congenital melanocytic nevi, and the remaining one-third have numerous lesions but no giant lesions. Most patients present with neurological features early in life, which can be secondary to intracranial hemorrhages (bleeding in the brain), impairment of cerebrospinal fluid circulation (fluid around the brain and spinal cord), and/or malignant transformation of the melanocytes.
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. Source: Genetic and Rare Diseases Information Center (GARD), supported by ORDR-NCATS and NHGRI.