# Prenatal Fetal Neurocutaneous Melanosis: A Case Report and Literature Review

## TL;DR

This paper reports a rare prenatal case of Neurocutaneous Melanosis with no known genetic mutations, highlighting the importance of multimodal prenatal diagnosis.

## Contribution

The study presents a rare prenatal NCM case with no identified pathogenic mutations, contributing to understanding its genetic variability.

## Key findings

- Prenatal diagnosis of NCM was achieved using ultrasound, MRI, fetoscopy, and genetic testing.
- No pathogenic mutations, including NRAS and BRAF, were found in the case.
- The case provides data supporting the need for multimodal approaches in NCM diagnosis.

## Abstract

Neurocutaneous melanosis (NCM) is a rare congenital syndrome characterized by congenital melanocytic nevus of the skin with melanocytic deposits in the central nervous system. Patients with neurological symptoms have a poor prognosis and may die within years of symptom onset.

A fetus was found to have diffuse enhancement of cerebellar hemispheric echo at 23 weeks of gestation and amniocentesis was performed at 25 weeks of gestation. Fetal DNA was extracted from amniotic fluid for copy number variation sequencing (CNV‐seq) and Trio‐total whole‐exome sequencing (Trio‐WES). However, genetic tests did not reveal pathogenic mutations associated with this case phenotype. At 29 weeks of pregnancy, a fetoscopy examination was performed, and multiple scattered pigmentation spots were found on the skin of the fetus's back. At 31 weeks of pregnancy, the pregnant woman requested an induced abortion to terminate the pregnancy. Multiple areas of pigmentation can be seen on the skin of a stillborn fetus. Pathological examination confirmed a large amount of melanin deposition in the cerebellum tissue of the stillborn fetus.

We reported a rare case of prenatal NCM, but no known pathogenic mutations, such as NRAS gene mutations, were found. This confirmed that there might be no definite pathogenic mutations in the NCM case, providing important data support for the prenatal identification and diagnosis of NCM.

We reported a rare case of prenatal NCM, but no known pathogenic mutations, such as NARS gene mutations, were found. This confirmed that there might be no definite pathogenic mutations in the NCM case, providing important data support for the prenatal identification and diagnosis of NCM.

A multimodal prenatal diagnostic approach for Neurocutaneous Melanosis (NCM), integrating ultrasound, MRI, fetoscopy, and genetic testing, in a case with negative NRAS/BRAF mutations.