Diagnosis Congenital myasthenic syndrome (CMS)

A specialist needs to make a clinical diagnosis and carry out tests for Congenital myasthenic syndrome (CMS), which will include taking a clinical history and measuring the function and response of muscles and nerves to repeated stimulation.

Further tests are needed to exclude other causes of the symptoms, including specialised genetic investigations using DNA from a blood sample, and a muscle biopsy to exclude other similar muscle-wasting conditions. A final definite diagnosis is made through genetic analysis of a DNA sample.

Once a diagnosis of CMS is made, families should be referred to a specialist genetics centre for a full discussion of the genetic implications of the diagnosis. Prenatal diagnosis can be offered in a future pregnancy if the genetic mutation has been identified.