Spectrum of Clinical, Neuroimaging, and Cerebrospinal Fluid Features of Adult Neurocutaneous Melanocytosis.

Background: Neurocutaneous melanocytosis (NCM) is a poorly understood disease due to its rarity. This study aimedto summarize the characteristics of adult NCM and improvethe awareness of this disease. Methods: The clinical data of 13 adult patients with NCM were retrospectivelyreviewed, including neuroimages, cerebrospinal fluid (CSF), and histological features. Results: There were 9 males and 4 females. The mean age at symptom onset was 36.5years. The initial symptoms included intracranial hypertension in 8 patients and seizure in 4 patients. Ten patients had large and/or multiple congenital melanocytic nevi. MRI revealed hydrocephalus and diffuse thickening ofthe leptomeninges with T1 shortening in all patients. Post-contrast T1-weighted images showed diffuse linear enhancement of the leptomeninges. Lumbar punctures showed increased open pressure, and elevated protein levels and decreased glucose concentrations in CSF. Cells with intracytoplasmic coarse black granules were found in the CSF and were positive for S100, HMB45, and vimentin. Histopathology of the cutaneous lesions and meninges showed melanocytes but no evidence of malignant melanoma. Conclusion: Adult NCM patients present a diversity of clinical manifestations. Brain MRI showing diffuse thickening of the leptomeninges with T1 shortening is useful in diagnosing NCM. Heterocellular melanin may be of great value for early diagnosis of NCM in challenging cases.