Neurocutaneous Melanosis: An Illustrative Patient

Abstract

We present a newborn with an unremarkable birth history who presented with a giant congenital melanocytic nevus with a “bathing trunk” distribution, accompanied by multiple satellite nevi (Fig 1). Cranial magnetic resonance imaging revealed multiple hyperintense lesions of the brain parenchyma and leptomeninges (Fig 2), confirming the diagnosis of neurocutaneous melanosis. At 13 months, he developed a partial seizure with secondary generalization. He had been asymptomatic until then. Antiepileptic treatment with valproic acid was started. Subsequently he has had occasional seizures that have required antiepileptic readjustment but has otherwise been well. Currently he is 3 years of age and has been seizure-free for 18 months with only mild developmental delay and no apparent progression of his neurocutaneous melanosis. Discussion Congenital melanocytic nevi are proliferations of benign melanocytes that arise during embryogenesis. Neurocutaneous melanosis is a complication of congenital melanocytic nevi and consists of proliferation of melanocytes in the central nervous system and leptomeninges as well as in the skin. It occurs in 2.5-45% of patients with congenital melanocytic nevi, 1 and the risk factors include large congenital melanocytic nevus, multiple satellite nevi, and more than two medium-sized congenital melanocytic nevi. 2-4 Neurocutaneous melanosis can be either symptomatic (3-10% of infants and children with congenital melanocytic nevi 2 ) or asymptomatic. Symptoms usually present in the first 2 years of life as developmental delay and/or seizures, 2 and the prognosis of symptomatic individuals is poor. Neurocutaneous melanosis is best