Learn about NDM
What is NDM?
Non-dystrophic myotonia, or NDM, refers to a group of diseases that affect muscles. The number of people with NDM varies in different countries, but on average approximately 1 in every 100,000 people worldwide are affected by NDM, and it is therefore classed as a rare disease.1
There are several forms of NDM, however all types share a common symptom called myotonia. Myotonia means that one’s muscles are not able to relax immediately after they have been used.2 Myotonia may be experienced as stiffness, cramps or locking of your muscles during everyday tasks and activities. People with NDM may also experience pain and fatigue.3 Most people with NDM start to notice symptoms in childhood or early adulthood, however it may be some time before they are diagnosed.3
“Sometimes my muscles remain tense and stiff but, at the same time, they lose all strength and then I lose control.”— HJ, Paramyotonia congenita
What causes NDM?
NDM is caused by a mutation in a gene, which prevents muscles from relaxing normally.2 NDM is inherited, however the ways in which it is passed on depends on the type of NDM that you have.
Types of NDM
NDM is not a single disease, it is a group of disorders, which share similar symptoms. The four main types are commonly known as Becker myotonia congenita, Thomsen myotonia congenita, paramyotonia congenita (Eulenburg) or dyskalaemic periodic paralysis.1,4 If you or your doctor think you have NDM, it is important to work with your healthcare team to understand what type of NDM you have, so that you can manage your symptoms in the best way possible.
Figure below shows how people with different types of NDM typically experience their symptoms.
Can NDM be treated?
Most people with NDM can adapt the way they do things to manage their symptoms. If your symptoms are affecting your daily life, you may wish to seek further advice from a healthcare professional who specialises in rare conditions affecting the muscles, like NDM.
There is currently no cure for NDM, but you can learn more about managing the symptoms of NDM and how to find specialist healthcare advice.
- Hahn C, Salajegheh MK. Iran J Neurol 2016;15:46–53
- Matthews E et al. Brain 2010;133:9–22
- Vereb N. J Neurol. 2021; 268(5): 1708–1720
- Trivedi JR, et al. Brain 2013;136:2189–2200