What are neuromuscular disorders?

The term ‘neuromuscular disorders’ refers to a large group of conditions that affect either the muscles themselves, or the nerves controlling the muscles. Most conditions cause weakness, often progressive, and some also affect other parts of the body. Furthermore, the severity of these conditions vary significantly and affect people quite differently. Understanding the reason why a person has a muscle disorder will very much depend upon the particular type of condition they have.

Conditions fall into two major groups: inherited and acquired.

What is a genetic condition?

Every cell in our bodies carries over 30,000 genes, each one being responsible for instructing our bodies to produce a particular protein. The majority of neuromuscular conditions are due to an abnormality (mutation or fault) occuring on specific genes. The abnormality then prevents the body producing certain proteins required for normal muscle or nerve function.

Our genes come in pairs and we inherit one copy from each parent.

Why do I have a neuromuscular disorder?

In some of these disorders (e.g. myotonic dystrophy, facioscapulohumeral dystrophy), only one gene within a pair of genes is abnormal (this is called autosomal dominant inheritance) - therefore each child of the affected person has a 50% chance of inheriting the condition. It is most likely that the parent inherited the condition from one of his or her parents.

In other disorders (e.g. congenital and limb girdle muscular dystrophy, and spinal muscular atrophy), both conditions have to be faulty in order to cause the condition. This is called autosomal recessive inheritance. In this situation the affected person has inherited an abnormal gene from each parent but his or her parents are unaffected because they each have a functioning copy of the gene. However, children of a person who has inherited the condition this way are very unlikely themselves to inherit the condition since their other parent will, most likely, have passed on to them a normal functioning copy of the gene.

Boys with an X-linked disorder (e.g. Duchenne and Becker muscular dystrophy) have usually inherited the faulty gene from their mother. Women have two X chromosomes whereas men have one X and one Y. In general, a woman carrying the faulty gene will have few or no problems because she has a normal functioning gene on her other X chromosome. However, her son has a 50% chance of inheriting this faulty gene and developing the condition.

Should I tell anyone about my condition?

Yes, it is important to share the information with your family. As the conditions are complex it is important that people receive an accurate diagnosis. This will help decide the ways in which the conditions are managed, and also so that appropriate counselling (when the risks are explained to family members) can be given. While many different people are diagnosed as having these disorders (including babies, children and adults) many others will also be affected by a diagnosis. For example, relatives of a person with muscular dystrophy may themselves be carrying the faulty gene and will want to be tested - hence individual and family needs will vary.

What is an acquired condition?

An acquired disorder is not due to a genetic problem - it arises in an individual who has no family history of a similar problem. Muscle weakness may be due to a hormone problem, or to metabolic problems. In the idiopathic (unknown or uncertain cause) inflammatory myopathies it appears that the body’s immune system becomes confused and attacks its own muscle, causing weakness. It is important that these conditions are recognised and diagnosed as they respond to drug treatment.

In myasthenia gravis, the body also produces antibodies which damage the connection between nerves and muscles, producing weakness which tends to vary from day to day.

What are the effects of all these conditions?

All these conditions affect the muscles in some way and the majority are progressive with different muscle groups being affected. Their severity ranges from life threatening or shortening and severely disabling through to more moderate or mild types that have little or no effect on life span.

As a number of muscular conditions can involve other parts of the body, for example the heart, and because treatment is available you may be advised to have a regular heart check up.

All in all, for those with a dystrophy or other neuromuscular condition good, careful management is of vital importance. For more information on this topic, visit the Muscular Dystrophy Group’s website at:

www.muscular-dystrophy.org