Congenital Myasthenic Syndromes (CMS) are a clinically and genetically heterogeneous group of disorders that typically present with muscle weakness in the first decade of life, but often are either undiagnosed for prolonged periods, or misdiagnosed with other conditions, most commonly with seronegative myasthenia gravis.

CMS can be classified as pre-synoptic, synaptic, and post-synaptic depending on the genetic defects affecting proteins at the neuromuscular junction. The course of disease and the response to treatment varies depending on the subtype. The majority of CMS is caused by defects in the post-synaptic proteins, such as DOK7, MUSK, AGRN or LRP4 which are signaling proteins responsible for the development and maintenance of the neuromuscular junction.

A natural history observational study evaluating participant symptoms and quality of life to better understand disease activity in patients with CMS.

You may be eligible to participate if you:

• Are at least 2 years of age.
• Have been diagnosed with DOK7-, MUSK-, AGRN- or LRP4-CMS.
• Are taking CMS medications for at least 3 months.
• Should have at least mild symptoms (as reflected in a QMG score of ≥3).

After completing screening, eligible participants with CMS will be followed by investigators for up to 12 months. During this time data and feedback on symptoms, treatment and healthcare resource utilization will be collected.

There will be no study drug or intervention given to the participants; the investigators will be observing participants as they receive their specialists’ recommended treatment for their CMS.