Atypical case of a neurocutaneous melanosis with typical magnetic resonance imaging findings

Introduction: Neurocutaneous melanosis (OMIM-Nr.: 249400) is a rare, congenital, sporadic syndrome defined by numerous and/or large congenital nevi and melanocytic proliferation within the brain parenchyma and the leptomeninges. The incidence has been estimated to be approximately 1 in 20,000 newborns. Clinical consequences can be hydrocephalus, seizures, and developmental delay. The risk to develop a malignant melanoma is increased.

According to current research on literature you have to bear in mind neurological involvement on the basis of following criteria: Large or giant congenital nevi, especially if those are multiple and spread on the whole body, located in posterior midline location (head, neck, back), or associated with satellite nevi. Magnetic resonance imaging (MRI) is the imaging technology of choice.

Case Report: We report the case of a 6-month-old girl with a giant congenital melanocytic nevus on the back (10 × 12 cm) and one smaller hyperpigmented nevus (1 × 1 cm) located on the scalp. She presents muscular hypotonia with primary sucking weakness and mild statmotoric developmental delay. Furthermore facial dysmorphism such as expanded bridge of the nose, insinuated epicanthus, and low set ears was reported. Ultrasound scanning of the head and electroencephalogram were without pathological results.

The MRI shows abnormal T1-hyperintensity within the cerebellum, commissura anterior, hippocampus, and brainstem, typical for neurocutaneous melanosis.

Conclusion: Neurological involvement should not only be considered in cases of multiple or extensive congenital melanocytic nevi. Even if the cutaneous morphology does not fit the above-named criteria, MRI to work-up cerebral involvement could be advisable.

Multidisciplinary evaluation is fundamental to detect neurological symptoms early and to prevent malignant melanoma.