Neurocutaneous melanosis (NM) is a rare congenital syndrome characterized by the presence of multiple or large melanocytic nevi (moles or birthmarks) in association with benign or malignant pigment cell tumors of the leptomeninges (pia mater and arachnoid mater).
A rare disorder marked by the presence of multiple or large pigmented nevi on the skin and in the leptomeninges of the central nervous system.