A Natural History Study in Participants With Congenital Myasthenic Syndromes (CMS) Due to Mutations in DOK7, MUSK, AGRN, or LRP4

Participants will attend up to 4 study visits to collect clinical assessments. The assessments will evaluate participants' symptoms and quality of life to understand disease activity in patients with CMS due to mutations in DOK7, MUSK, AGRN, or LRP4. More information can be found here: https://clinicaltrials.argenx.com/cms

Inclusion Criteria: * Can understand the requirements of the study and can provide written informed consent/assent, and willingness and ability to comply with the study protocol procedures * Is male or female and aged ≥2 years at the time of providing informed consent/assent * Has a diagnosis of CMS due to biallelic pathogenic mutations in DOK7 or any pathogenic mutations in MUSK, AGRN, or LRP4 * Has a total Quantitative Myasthenia Gravis (QMG) score of ≥3 (applies only to participants aged ≥6 years) * For participants taking oral beta agonists (eg, albuterol, salbutamol, ephedrine), participant must have been receiving the medication for ≥3 months before screening/baseline Exclusion Criteria: * Known medical condition that would interfere with an accurate assessment of CMS, in the investigator's opinion * Is currently participating in any interventional clinical study with a study drug at the time of providing informed consent/assent * Diagnosis of CMS due to mutation of any gene other than DOK7, MUSK, AGRN, or LRP4