Congenital Myasthenic Syndrome

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

The purpose of this study is to assess the safety and tolerability of ARGX-119 in adult participants with DOK7- Congenital Myasthenic Syndromes. The study will also assess how ARGX-119 is processed by the body (pharmacokinetics), how the immune system reacts to it (immunogenicity), and how it may improve the way patients feel and function. After the screening period, eligible participants will be randomized in a 4:1 ratio to receive intravenous infusions of ARGX-119 or placebo during the double-blinded treatment period. Participants will then enter the follow-up period. After the follow-up period, participants may enrol in the active-treatment period, where they will receive open-label ARGX-119. The full duration of the study is approximately 38 months.

Patients with Congenital Myasthenic Syndrome will be treated with Mesenchymal Stem Cell Exosome solution.

The Congenital Muscle Disease Patient and Proxy Reported Outcome Study (CMDPROS) is a longitudinal 10 year study to identify and trend care parameters, adverse events in the congenital muscle diseases using the Congenital Muscle Disease International Registry (CMDIR) to acquire necessary data for adverse event calculations (intake survey and medical records curation). To support this study and become a participant, we ask that you register in the CMDIR. You can do this by visiting www.cmdir.org. There is no travel required. The registry includes affected individuals with congenital muscular dystrophy, congenital myopathy, and congenital myasthenic syndrome and registers through the late onset spectrum for these disease groups. The CMDIR was created to identify the global congenital muscle disease population for the purpose of raising awareness, standards of care, clinical trials and in the future a treatment or cure. Simply put, we will not be successful in finding a treatment or cure unless we know who the affected individuals are, what the diagnosis is and how the disease is affecting the individual. Registering in the CMDIR means that you will enter demographic information and complete an intake survey. We would then ask that you provide records regarding the diagnosis and treatment of CMD, including genetic testing, muscle biopsy, pulmonary function testing, sleep studies, clinic visit notes, and hospital discharge summaries. Study hypothesis: 1. To use patient and proxy reported survey answers and medical reports to build a longitudinal care and outcomes database across the congenital muscle diseases. 2. To generate congenital muscle disease subtype specific adverse event rates and correlate with key care parameters.