Muscular dystrophy (MD) is a group of muscle diseases that results in increasing weakening and breakdown of skeletal muscles over time. The disorders differ in which muscles are primarily affected, the degree of weakness, how fast they worsen, and when symptoms begin. Many people will eventually become unable to walk.
Muscular dystrophy is the name given to a group of inherited neuromuscular conditions. These conditions cause weakness and wasting of the muscles. This muscle wastage gets worse over time, and is not reversible.
There are more than 30 different types of muscular dystrophy. Most are caused by changes to genes involved in providing strength to the muscle structure.
There are around 30 other neuromuscular conditions that can be confused with muscular dystrophy due to their having similar symptoms. However, these conditions are caused by a different mechanism.
What causes muscular dystrophy?
Many genes help to make the proteins that protect muscle fibres from damage. Muscular dystrophy occurs if one of these genes does not work properly.
Each type of muscular dystrophy is caused by a different change in a gene. Some of these gene changes are inherited from a parent. Some of them are new changes that occur early in development. These are known as spontaneous or ‘de novo’ gene changes.
Spontaneous gene changes are not inherited, but they can be passed on to the next generation.
Types of muscular dystrophy
There are more than 30 different types of muscular dystrophy. The main types are:
- Duchenne muscular dystrophy
- Becker muscular dystrophy
- congenital muscular dystrophy
- limb-girdle muscular dystrophy
- facioscapulohumeral muscular dystrophy
- myotonic dystrophy
- oculopharyngeal muscular dystrophy
- Emery-Dreifuss muscular dystrophy.
Some of these types of muscular dystrophy are further divided into sub-types. For example, there are more than 20 types of limb-girdle muscular dystrophy.
From one type of muscular dystrophy to another, there is variation in:
- the severity of the muscle degeneration
- which muscles degenerate.
Symptoms of Duchenne muscular dystrophy
Duchenne muscular dystrophy is not usually noticeable before the age of two or three. Symptoms and signs include:
- delayed walking age
- frequent falls, difficulty rising up from the ground or going up hills or stairs
- difficulty running and jumping
- well-developed or excessively large calf muscles. Other muscles are poorly developed
- a waddling walk
- a sway-back (‘lordosis’)
- a tendency to stand and walk on the forefoot, with the heel off the ground. This is often called ‘toe-walking’.