BACKGROUNDCongenital myasthenic syndromes are a group of rare disorders that are clinically and genetically heterogeneous and caused by mutations in the genes encoding proteins of the neuromuscular junction. Here, we described a Chinese family that presented with phenotypes of classic slow-channel congenital myasthenic syndrome (SCCMS).

METHODSClinical characteristics and electrophysiological features of three patients from a Chinese family were examined, and next-generation sequencing followed by direct sequencing was carried out.

RESULTSThe patients revealed variability in clinical and electrophysiological features. However, weakness, scoliosis, and repetitive-compound muscle action potential were found in all affected members in the family. A heterozygous C>T missense mutation at nucleotide 865 in acetylcholine receptor epsilon-subunit (CHRNE) gene that causes a leucine-to-phenylalanine substitution at position 289 (L289F) was found.

CONCLUSIONSWe reported a SCCMS family of Chinese origin. In the family, classical clinical phenotype with phenotypic variability among different members was found. Genetic testing could help diagnose this rare disease.