RESUMO
INTRODUCTION: In this study, we present a case of primary diffuse leptomeningeal melanomatosis (PDLM), without neurocutaneous melanosis syndrome. A female patient (age: 14 years) presented with headache, nausea, vomiting, vertigo, diplopia, and lower limb weakness. The magnetic resonance imaging (MRI) showed leptomeningeal isointensity on T1- and T2-weighted images and hyperintensity on fluid attenuation inversion recovery (FLAIR) sequences. Definitive histological examination showed a densely cellular tumor, characterized by irregular clusters of large pleomorphic cells and melanin in tumor cells. Adjuvant therapy was refused by the parents, and the patient died within six months. Primary diffuse leptomeningeal melanomatosis is recognized as an uncommon and malignant melanoma affecting the central nervous system. In case comorbidities are not diagnosed in patients with unusual symptoms of meningitis, diagnostic methods such as cerebrospinal fluid analysis and central nervous system biopsy can be helpful in identifying other underlying conditions.