Pearls & Oy-sters: Primary Diffuse Leptomeningeal Melanocytosis A Diagnostic Conundrum

Primary diffuse leptomeningeal melanocytosis (PDLM) is an extremely rare CNS tumor with nonspecific clinicoradiologic features that overlap considerably with aseptic meningitis posing significant diagnostic and therapeutic challenges. We present one such case report of a patient treated empirically at first presentation as aseptic viral meningitis based on MRI and CSF analysis. Diagnosis of PDLM was established subsequently through meningeal biopsy that demonstrated a melanocytic tumor with fine granular melanin pigment without significant mitoses. Her systemic and ocular examination was unremarkable. Whole-body 18F-fluorodeoxyglucose PET/CT (FDG-PET/CT) did not identify any other primary site. Following ventriculoperitoneal shunt to relieve hydrocephalus, she was treated with definitive craniospinal irradiation plus whole-brain boost and remains stable on periodic clinicoradiologic surveillance. Optimal management of PDLM lacks consensus with role of radiotherapy, chemotherapy, targeted therapy and immunotherapy being controversial.

Automated summary

Primary diffuse leptomeningeal melanocytosis (PDLM) is a rare CNS tumor that presents diagnostic and therapeutic challenges due to its overlapping features with aseptic meningitis. This case report describes a patient initially treated for viral meningitis based on MRI and CSF analysis, but later diagnosed with PDLM through meningeal biopsy. The patient underwent ventriculoperitoneal shunt and craniospinal irradiation, and remains stable on regular surveillance. Optimal management of PDLM is controversial, with the role of radiotherapy, chemotherapy, targeted therapy, and immunotherapy still being debated.