Neurocutaneous melanosis.

Neurocutaneous melanosis is a rare neurocutaneous syndrome that is associated with a high rate of mortality early in life. Individuals with large cutaneous melanocytic nevi (LCMN) are at risk, especially when the nevi are posterior, midline and accompanied by satellite nevi. Disrupted production and migration of melanocytic precursors from neural crest likely are responsible. Although the cutaneous lesions are at risk for melanoma, the most likely source of morbidity and mortality comes from "benign" melanocytic proliferation in the brain or central nervous system melanoma. Seizures and hydrocephalus are the common neurologic manifestations and typically arise in the first years of life. Brain magnetic resonance imaging in infants before myelination has matured is most sensitive for detecting abnormal melanosis in the brain, which preferentially involves the leptomeninges, cerebellum and anterior temporal lobes. Treatment is symptomatic and death occurs in many within 3 years of onset of neurologic symptoms. This prognosis may limit the extent to which extensive procedures or interventions are undertaken.