Objective: To explore the genetic basis for a female patient featuring unstable head upright and hypotonia of limbs.
Methods: The child was examined clinically. Peripheral blood samples of the child, her parents and siblings were collected. Genomic DNA was extracted and subjected to next generation sequencing (NGS). Suspected variant was verified by Sanger sequencing and bioinformatic analysis.
Results: DNA sequencing found that the patient has carried a de novo heterozygous c.354C>A (p.N118K) variant of the CHRND gene, which was not found in her parents and sibling. Bioinformatics analysis predicted that the variant was likely to be pathogenic. Literature review suggested that the phenotype of the patient was very similar to previously reported ones.
Conclusion: The child was diagnosed with slow-channel congenital myasthenic syndrome (SCCMS) type 3A caused by heterozygous variant of the CHRND gene. NGS has provided a powerful tool for the diagnosis of such disorders.