Muscular Dystrophies - An Overview

What is muscular dystrophy?

Muscular dystrophy is the name given to a group of disorders which cause muscle weakness. There are many different types of muscular dystrophy, which vary as to how mild or severe they are, and which muscles they affect. The different types of muscular dystrophy are explained later in this article.

What causes muscular dystrophy?

The cause is genetic. In each type of muscular dystrophy, there is an alteration in a gene. This then causes a change in one of the proteins (chemicals) which is needed for the muscles to work properly.

What are genes?

Genes are made from a biological material called DNA. Genes control the way each cell functions and the proteins it makes. Some genes control the proteins needed for muscle functioning - it is these genes which are involved in causing muscular dystrophy.

Because muscular dystrophy has a genetic cause, it can be inherited - meaning that it can occur in more than one person in a family, and can be passed on from parent to child. In some cases, family members may carry the muscular dystrophy gene even if they do not have muscle weakness. However, in other cases the genetic alteration occurs just in one individual, with the rest of the family having normal genes. DNA tests and genetic specialists can help to find out the genetic cause of the muscular dystrophy in each individual case. Also, it may be possible to offer tests which would check whether anyone else in the family has the gene.

What are the symptoms of muscular dystrophy?

The main symptom of muscular dystrophy is muscle weakness. This varies greatly between the different types of muscular dystrophy.

Symptoms may start anywhere between birth and middle age, depending on which type of muscular dystrophy is involved. In young babies, the muscle weakness may be noticed as 'floppiness' of the baby. In older babies and young children, the weakness may show up as as the child having a delay in 'motor milestones', meaning a delay in learning to hold up their heads, sit up, crawl or walk. (But note that there are many other causes of delayed motor milestones apart from muscular dystrophy.)

There are also differences as to which parts of the body are affected. Different types of muscular dystrophy affect different muscle areas (known as muscle groups) of the body - see the picture below.

The muscle weakness itself may be mild, moderate or severe. The different types of muscular dystrophy vary as to how quickly or slowly the weakness progresses.

Sometimes there may be symptoms other than muscle weakness. These are:

• Contractures - where joints are tight, due to tightness of the muscles or reduced movement of the joints.
• Muscle wasting - where the muscles become thin.
• Muscle hypertrophy - where the muscles are bulkier than normal, even though they work less well.

What are the different types of muscular dystrophy?

Duchenne muscular dystrophy

The most common and most severe type of muscular dystrophy is a type called Duchenne muscular dystrophy. This causes muscles to become weak, mainly in the legs and upper arms. The weakness starts early in childhood and gradually increases, affecting the child's ability to walk. Generally, boys with Duchenne muscular dystrophy need to use a wheelchair from around the age of twelve years. From their late teenage years there can be complications such as weakness of the breathing or heart muscles, which need treatment.

The heart and breathing problems eventually lead to an earlier death, so that boys with Duchenne muscular dystrophy generally live into their twenties or late twenties but not beyond.

Duchenne muscular dystrophy usually only affects boys. Rarely, girls can be affected too - if so, it is a much milder condition in girls.

If a child has Duchenne muscular dystrophy, then women and girls in the family could be carrying the Duchenne gene - although it is equally possible that they have normal genes. It is possible to test family members to see if they have the Duchenne gene.

There is a separate leaflet called Duchenne Muscular Dystrophy for more information.

Becker muscular dystrophy

Becker muscular dystrophy is much less severe than Duchenne muscular dystrophy, although the two types have the same muscle groups affected. Symptoms start in the teenage years or early twenties. The weakness progresses slowly, so that in their 40s and 50s, men with this condition may have difficulty walking. At this stage, weakness of the heart and breathing muscles can occur and extra treatment may be needed.

Becker muscular dystrophy usually affects only boys. However, girls in the family might carry the Becker gene, and can be tested for this.

Facioscapulohumeral muscular dystrophy

Facioscapulohumeral muscular dystrophy (FSH) is also called Landouzy-Dejerine or facioscapuloperoneal muscular dystrophy. FSH can affect both men and women.

FSH affects the muscles of the face, shoulder and upper arm. Sometimes the legs may be affected too. Symptoms usually start around age 40-50. The degree of muscle weakness varies a lot from person to person. About 3 in 10 people with FSH don't notice any symptoms. About 1 in 10 people with FSH eventually require a wheelchair. Most people with FSH have symptoms somewhere in between these two extremes.

Limb girdle muscular dystrophy

The limb girdle muscular dystrophies cause weakness in the large muscles around the top of the arms and legs. These muscles are also called the 'shoulder and pelvic girdles'. There are many different types of limb girdle muscular dystrophies, which affect both men and women. The symptoms and muscle weakness vary a great deal, depending on which particular form of limb girdle muscular dystrophy you have.

Emery-Dreifuss muscular dystrophy

Emery-Dreifuss muscular dystrophy starts in childhood or adolescence. It can affect the muscles of the shoulders and upper arms, making it difficult to lift heavy objects. Also, the muscles in the lower leg are affected, which may cause tripping over when walking. Contractures (tightness) of the muscles and joints can also occur. Emery-Dreifuss muscular dystrophy usually progresses (increases) very slowly. People who have this condition may need a wheelchair later in life.

Emery-Dreifuss muscular dystrophy may also affect a part of the heart muscle which controls the heart rate. This may cause a slow heart beat and symptoms of giddiness or fainting. This problem can be successfully treated with a heart pacemaker.

Congenital muscular dystrophy

Congenital muscular dystrophy is rare (affecting about 1 in 50,000 babies). It is actually a group of conditions which cause muscle symptoms early in life - within the first six months of birth. The first symptoms are poor head control, muscle weakness (making the the baby seem floppy), or dislocated hips. Later symptoms may be a delay in the child crawling, standing and walking; or tightness (contractures) in some joints.

Oculopharyngeal muscular dystrophy

Oculopharyngeal muscular dystrophy (OPMD) usually starts around the 50s or 60s. It causes a weakness in the eye and throat muscles. The first symptoms are droopy eyelids and difficulty swallowing. Later on, after many years, mild limb weakness around the shoulders and hips may also develop.

How is muscular dystrophy diagnosed?

Usually it is first suspected because of symptoms: a muscle weakness is noticed by the patient, family or a doctor. Also, if a child has delayed motor milestones (as mentioned above), a doctor may advise testing for muscular dystrophy, even though the problem could be due to another cause.

Muscular dystrophy may be diagnosed using one or more of the following tests:

• A blood test for creatine kinase - in many types of muscular dystrophy, the blood level of creatine kinase (also called CK) is very high.
• An EMG (electromyogram) - this is a recording of the electrical activity in a muscle.
• A muscle biopsy - this involves taking a small sample of muscle under local anaesthetic. The sample is examined under the microscope and the muscle proteins may be tested.
• Genetic analysis - this involves a testing a person's DNA using a blood sample. It can detect many (not all) cases of muscular dystrophy.

What else could it be?

There are other medical conditions which cause muscle weakness, and might seem similar to muscular dystrophy. These are:

• Conditions called 'myopathies' - in which there is muscle weakness. Some myopathies are temporary problems and are not genetic.
• Other conditions called 'neuromuscular disorders'. This is the name for a group of conditions which affect nerves, muscles or both. See the further information section.
• Myotonic dystrophy. This may be classified as a type of muscular dystrophy or as a neuromuscular disorder. It affects the 'small' muscles, such as those in the face, jaw, neck, and hands. Myotonic dystrophy may start at any age from birth to old age. It can affect both men and women.
• Distal myopathies. These are very rare forms of muscle weakness affecting the 'distal' muscles, which are those of the hands and feet. There are different types. Most are very mild.

How is muscular dystrophy treated?

There is no cure for muscular dystrophy, although there are treatments which can help. The treatment offered will depend on what type of muscular dystrophy you (or your child) has. You may be referred to a specialist, who will be able to give you more information on the condition and on the treatment options. See further information below, for more details.

As a general guide, treatment may involve:

• Firstly, obtaining an accurate diagnosis of the condition. You may see a doctor who specialises in muscular or genetic conditions. In some cases, the specialist may suggest that other family members be tested to see if they carry a muscular dystrophy gene.
• Physiotherapy to help keep the joints mobile.
• For some types of muscular dystrophy such as Duchenne type, treatment with steroid medicine helps to maintain muscle strength.
• Practical aids or help may be needed, for example, a splint, wheelchair or equipment for the home.
• For some types of muscular dystrophy, regular checkups are needed to assess and treat any complications.

Further help and information

The Muscular Dystrophy Campaign

61 Southwark Street, London SE1 0HL
Helpline: 0800 652 6352
Web: www.muscular-dystrophy.org
This is a UK charity for all muscular dystrophies, neuromuscular disorders and related conditions. It funds research, offers help and advice, and provides information and support.