A Prospective Natural History and Outcome Measure Validation Study of Congenital Myasthenic Syndromes

* INCLUSION CRITERIA: In order to be eligible to participate in this study, an individual must meet all of the following criteria: * Stated willingness to comply with all study procedures and availability for the duration of the study * Male or female, aged \>= 6 months of age * Clinically stable as evidenced by medical record review and remote screening questionnaire * Genetically confirmed congenital myasthenic syndrome (pathogenic or likely pathogenic variants identified by CLIA testing in an established CMS-related gene including but not limited to DOK7, COLQ, CHRNE, RAPSN, CHAT, GFPT1, DPAGT1 OR pathogenic/likely pathogenic variant in combination with a variant of uncertain significance (VUS) AND additional clinical supporting evidence of CMS). * Agreement to adhere to Lifestyle Considerations throughout study duration * Ability of subject to understand and the willingness to provide informed consent (\>=18 years of age) and assent (\>=7 years of age). EXCLUSION CRITERIA: * Received gene transfer therapy * Pregnant women (prior to enrollment) * Ongoing medical condition or medication use that is deemed by the Principal Investigator to interfere with the conduct or assessments of the study or safety of the subject.