Late-diagnosed congenital myasthenic syndrome due to a CHRNE mutation: a case report

Abstract

Congenital myasthenic syndromes (CMS) comprise a heterogeneous group of inherited disorders caused by genetic defects affecting neuromuscular junction transmission. Clinical manifestations range from isolated ocular symptoms to severe neonatal respiratory insufficiency. Despite symptom onset early in life, CMS is frequently underdiagnosed or misdiagnosed, most commonly as myasthenia gravis (MG), leading to prolonged diagnostic delay. We report a young woman with fluctuating muscle weakness and eyelid drooping since early childhood who had been followed for years with a diagnosis of seronegative MG. In adulthood, genetic analysis identified a homozygous nonsense mutation in the CHRNE gene, establishing the diagnosis of CMS. This case highlights the diagnostic challenges posed by CMS due to its clinical overlap with MG and emphasizes the critical role of genetic testing in patients with seronegative, treatment-resistant neuromuscular weakness.