Question: What is (are) Neurocutaneous melanosis ?
Answer: 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: GARD

Question: What are the symptoms of Neurocutaneous melanosis ?
Answer: What are the signs and symptoms of Neurocutaneous melanosis? The Human Phenotype Ontology provides the following list of signs and symptoms for Neurocutaneous melanosis. If the information is available, the table below includes how often the symptom is seen in people with this condition. You can use the MedlinePlus Medical Dictionary to look up the definitions for these medical terms. Signs and Symptoms Approximate number of patients (when available) Cognitive impairment 90% Generalized hyperpigmentation 90% Hypertrichosis 90% Melanocytic nevus 90% Seizures 90% Thickened skin 90% Abnormality of neuronal migration 7.5% Abnormality of retinal pigmentation 7.5% Aplasia/Hypoplasia of the cerebellum 7.5% Arnold-Chiari malformation 7.5% Behavioral abnormality 7.5% Chorioretinal coloboma 7.5% Cranial nerve paralysis 7.5% Dandy-Walker malformation 7.5% EEG abnormality 7.5% Encephalitis 7.5% Hemiplegia/hemiparesis 7.5% Intracranial hemorrhage 7.5% Melanoma 7.5% Meningocele 7.5% Renal hypoplasia/aplasia 7.5% Syringomyelia 7.5% Thrombophlebitis 7.5% Arachnoid cyst 5% Choroid plexus papilloma 5% Hydrocephalus 5% Meningioma 5% Death in infancy - Mental deterioration - Numerous congenital melanocytic nevi - Sporadic - The Human Phenotype Ontology (HPO) has collected information on how often a sign or symptom occurs in a condition. Much of this information comes from Orphanet, a European rare disease database. The frequency of a sign or symptom is usually listed as a rough estimate of the percentage of patients who have that feature. The frequency may also be listed as a fraction. The first number of the fraction is how many people had the symptom, and the second number is the total number of people who were examined in one study. For example, a frequency of 25/25 means that in a study of 25 people all patients were found to have that symptom. Because these frequencies are based on a specific study, the fractions may be different if another group of patients are examined. Sometimes, no information on frequency is available. In these cases, the sign or symptom may be rare or common.
Source: GARD