Congenital Myasthenic Syndrome From a Single Center: Phenotypic and Genotypic features.

Background: Congenital myasthenic syndrome is a group of rare genetic disorders affecting transmission across the neuromuscular junction. Patients present with variable ocular, bulbar, respiratory, and extremity weakness that may respond to symptomatic therapies.

Methods: We identified 18 patients with congenital myasthenic syndrome from a pediatric neuromuscular center over a decade. Through a retrospective chart review, we characterize demographic profile, clinical features, genetic variants, treatment, and follow-up of these patients.

Results: Patients had the following genetic subtypes: (6), (2), (2), (2), (1), (1), (1), (1), (1), and (1). The phenotype varied based on the genetic variants, though most patients have generalized fatigable weakness affecting ocular, bulbar, and extremity muscles. There was a significant delay in the diagnosis of this condition from the onset of symptoms. Although most patients improved with pyridostigmine, some subtypes showed worsening with pyridostigmine and others benefited from albuterol, ephedrine, or 3,4-diaminopyridine treatment.

Conclusion: Increasing recognition of this rare syndrome will lead to early diagnosis and prompt treatment. Prompt utilization of genetic testing will identify novel variants and the expanding phenotype of this condition.