Primary leptomeningeal melanocytosis in a 10-year-old girl: a challenging diagnosis with a poor prognosis.

Primary leptomeningeal melanocytosis is rarely encountered in the pediatric population. Despite being considered a nonmalignant condition, it uniformly carries a poor prognosis given the ineluctable progression of meningeal infiltration. The case of a previously healthy 10-year-old girl who was first thought to suffer from recurrent hemiplegic migraine is reported. She later developed insidious subacute hydrocephalus. Meningeal biopsy performed during shunt insertion demonstrated an unexpectedly large number of melanocytes consistent with meningeal melanocytosis. Subsequently, the child developed recurrent shunt dysfunction and showed evidence of malignant transformation. The steps to reaching the proper diagnosis are discussed, and the current literature on this rare clinical entity as well as on related central nervous system melanocytic lesions that can occur in the pediatric population is reviewed.