# Genetic analysis of a family affected by congenital myasthenic syndrome due to a Novel mutation in the SLC5A7 gene

## TL;DR

A novel deletion in the SLC5A7 gene causes congenital myasthenic syndrome in a Chinese family, with symptoms improving after treatment.

## Contribution

The study reports a novel exon deletion in the SLC5A7 gene as a cause of congenital myasthenic syndrome.

## Key findings

- A heterozygous deletion spanning exons 1–9 of the SLC5A7 gene was identified in a patient with congenital myasthenic syndrome.
- The deletion was confirmed in the patient’s mother and brother through QPCR.
- Treatment with pyridostigmine improved clinical symptoms of myasthenia.

## Abstract

Mutations in the SLC5A7 gene cause congenital myasthenia, a rare genetic disorder. Mutation points in the SLC5A7 gene differ among individuals and encompass various genetic variations; however, exon deletion variants have yet to be reported in related cases. This study aims to explore the clinical phenotype and genetic traits of a patient with congenital myasthenic syndrome due to SLC5A7 gene variation and those of their family members.

We describe a case of a Chinese male with congenital myasthenic syndrome presenting fluctuating limb weakness. Genetic testing revealed a heterozygous deletion mutation spanning exons 1–9 in the SLC5A7 gene. QPCR confirmed a deletion in exon 9 of the SLC5A7 gene in the patient’s mother and brother. Clinical symptoms of myasthenia improved following treatment with pyridostigmine.

Exons 1, 5, and 9 of the SLC5A7 gene encode the choline transporter’s transmembrane region. Mutations in these exons can impact the stability and plasma membrane levels of the choline transporter. Thus, a heterozygous deletion in exons 1–9 of the SLC5A7 gene could be the pathogenic cause for this patient. In patients exhibiting fluctuating weakness, positive RNS, and seronegativity for myasthenia gravis antibodies, a detailed family history should be considered, and enhanced genetic testing is recommended to determine the cause.