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. The typical cutaneous lesions are present at birth. Neurological features typically present in the first or second year. Intracranial hypertension is the most common presentation, along with seizures, decreased alertness, and cranial nerve dysfunction.The underlying cause, while not completely understood, is believed to be a primary defect in the neural crest.