Primary Amelanotic Leptomeningeal Melanomatosis in a Child: A Rare but Severe Disease

Abstract

Primary leptomeningeal melanomatosis (PLM) is a rare and aggressive form of nonmetastatic invasion of leptomeninges by malignant melanocytic cells. Clinical presentation includes nonspecific meningism with various forms of cerebrospinal fluid circulation or absorption disorders leading to hydrocephalus. A 5-year-old child with PLM without neurocutaneous melanosis presented with cystic enlargement of the brainstem surrounding cisterns and hydrocephalus requiring occipitoaxial decompression and endoscopic cystostomy. Initial cerebrospinal fluid cytology screening and frontal meningeal and brain biopsy specimens showed negative results. The diagnosis of unpigmented (amelanotic) malignant melanocytic cells was made after a biopsy specimen of the bulbar leptomeninges was obtained. Despite continuous management of hydrocephalus and chemotherapy, the disease progressed, and the patient died 11 months after diagnosis. To the best of our knowledge, this is the first report of an amelanotic form of PLM without association of neurocutaneous melanosis in a child. This case report illustrates the difficulty of diagnosis in the absence of cutaneous lesions and lack of melanin.