# Pelizaeus-Merzbacher Disease as a Cause of Early-Onset Developmental Delay: A Case Report

## TL;DR

This case report describes a rare genetic disorder causing developmental delay in a male patient and highlights a new genetic mutation and potential treatment with biotin.

## Contribution

The paper identifies a rare PLP1 gene deletion and suggests biotin as a potential treatment for Pelizaeus-Merzbacher disease.

## Key findings

- A deletion in exon 16 of the PLP1 gene (c.330C>T) was identified in a PMD patient.
- Biotin may help improve symptoms in PMD patients due to lack of curative treatments.
- Early diagnosis of PMD is crucial for managing developmental delays.

## Abstract

Pelizaeus-Merzbacher disease (PMD) is a rare X-linked hypomyelinating leukodystrophy disorder caused by a mutation in the proteolipid protein 1 (PLP1) gene which is responsible for myelin formation in the central nervous system. We report a case of PMD in a male patient who initially presented with developmental delay at three months and was ultimately diagnosed at 10 years and 7 months of age. We aim to describe the initial presentation, clinical course of PMD and the investigations that aid in diagnosis so that future cases may be identified earlier. During the investigative workup of our patient, a deletion of exon 16 - an extremely rare heterozygous nucleotide variation, c.330C>T (p.D110D) - was identified, the pathogenicity of which has not been previously documented in the literature. In our report, we also aim to highlight the potential use of biotin in improving symptoms in such patients as there is currently no curative treatment available.