Muscular dystrophy - Types of muscular dystrophy

There are many different types of muscular dystrophy (MD). All cause muscle weakness, but the areas affected and the severity of the symptoms are different.

Typical symptoms of some of the most common types of MD are explained below. The Muscular Dystrophy Campaign also provides a list of specific neuromuscular conditions.

Duchenne muscular dystrophy

Because of the way it's inherited (see causes of muscular dystrophy), Duchenne MD mostly affects boys. Girls can occasionally be affected, but the condition tends to be milder in females.

Children with Duchenne MD usually start to have noticeable symptoms between the ages of one and three years. The muscles around their pelvis and thighs tend to be affected first and often appear bulkier than normal.

A child with Duchenne MD may:

• have difficulty walking, running or jumping
• have difficulty standing up
• learn to speak later than usual
• be unable to climb the stairs without support
• have behavioural or learning difficulties

Children with Duchenne MD may need a wheelchair by the time they are 8-14 years old, as their muscles weaken and they lose the ability to walk. They can also develop scoliosis, which is where the spine begins to curve sideways. This can lead to one shoulder or hip being higher than the other.

By the mid-teens, some people with Duchenne MD will develop dilated cardiomyopathy. This is where the condition affects the heart muscles, causing the chambers of the heart to enlarge and the heart walls to become thinner.

By their late teens or early 20s, people with Duchenne MD can begin to have breathing problems. The condition can affect the intercostal muscles (muscle tissue between the ribs) and the diaphragm (main muscle between the chest and abdomen used during breathing). 

Once the heart and respiratory muscles are damaged, Duchenne MD becomes life threatening. With medical care, most people with Duchenne MD die from heart or respiratory failure before or during their 30s.

Myotonic dystrophy

As with other types of muscular dystrophy, myotonic dystrophy involves progressive muscle weakness and muscle wasting. However, it is often the smaller muscles that are affected first, such as those in the face, jaw and neck.

Myotonic dystrophy can appear at any time between birth and old age. It affects the same number of men and women.

As well as muscle weakness and wasting, symptoms can include:

• muscle stiffness (myotonia)
• clouding of the lens in the eye (cataracts)
• excessive sleeping or sleepiness
• swallowing difficulties (dysphagia)
• behavioural and learning problems in children
• a slow and irregular heartbeat (cardiac arrhythmia)

Myotonic dystrophy is very variable and sometimes gets worse only very slowly, with little change over long periods of time. However, it can become more severe as it is passed down through the generations in a family.

Some people with myotonic dystrophy may never have a significant disability, although their heart rate will need to be monitored for abnormalities. This is because there is a risk of a serious problem where the electrical impulses that control the heartbeat travel too slowly through the heart. In some people, the condition can also cause cataracts to develop at a younger age than usual.

Life expectancy for people with myotonic dystrophy can vary considerably. Many people have a normal life expectancy, but people with the more severe congenital form of the condition (present from birth) may die while still a newborn baby or only survive for a few years.

Some people who first develop symptoms as a child or teenager may also have a shortened life expectancy.

Most deaths related to myotonic dystrophy are related to pneumonia, breathing problems or heart problems.

It is important for someone with myotonic dystrophy to know about their condition and to tell any doctor they see that they are affected, as it can lead to difficulties with general anaesthetics and childbirth.

Facioscapulohumeral muscular dystrophy

Facioscapulohumeral MD can affect both men and women. It tends to affect men slightly more than women, although the reason for this is unclear. Men also tend to be affected earlier and more severely.

About one in three people with facioscapulohumeral MD are unaware of any symptoms until well into adulthood, but others develop problems in early childhood. The condition tends to progress slowly.

Symptoms in your child may include:

• sleeping with their eyes slightly open
• they cannot squeeze their eyes tightly shut
• they cannot purse their lips (for example, to blow up balloons)

Teenagers or adults may have shoulder aches, rounded shoulders or thin upper arms. As the condition progresses, it usually affects the muscles in the:

• face (facio)
• shoulders (scapula)
• upper arms (humeral)
• upper back
• calves

Around half of all people with facioscapulohumeral MD develop weakness in their leg muscles and 1 or 2 in every 10 people with the condition will eventually need a wheelchair.

Facioscapulohumeral MD can develop unevenly, so the muscles on one side of the body may be affected more than the other.

As the condition progresses slowly, it does not usually shorten life expectancy.

Becker muscular dystrophy

Like Duchenne MD, Becker MD mostly affects boys. Becker MD also affects similar areas of the body to Duchenne MD, although the symptoms tend to be less severe.

Symptoms of Becker MD usually begin in childhood, but they are often relatively mild at this point. For example, a child with the condition may:

• learn to walk later than usual
• have muscle cramps when exercising
• struggle with sport at school

During late childhood or early adulthood, affected individuals will often first find that they have difficulty running, walking quickly and climbing stairs. As they get older, they may find it difficult to lift objects above waist height. 

They will often eventually require a wheelchair by the time they are 40-50 years old, but this is variable. For example, one person with Becker MD may become unable to walk at 16 years, while another person may walk until they are 80.

If you have Becker MD, you are also at risk of developing dilated cardiomyopathy and breathing problems. However, Becker MD progresses more slowly than Duchenne MD, and those with the condition often have a normal lifespan.

Limb-girdle muscular dystrophy

Limb-girdle MD is the name given to a number of related conditions that cause weakness in the big muscle groups at the base of the arms and legs (around the shoulders and hips).

The first symptoms are often mobility problems affecting the hip girdle. It then progresses to the shoulder girdle ("girdle" means the bones around the shoulder or hip).

Symptoms of limb-girdle MD usually begin in late childhood or early adulthood, although the condition can affect people younger or older than this, depending on the specific type. The condition affects both sexes equally.

If you have limb-girdle MD, you may experience:

• muscle weakness in your hips, thighs and arms
• loss of muscle mass in the affected areas
• back pain 
• heart palpitations or irregular heartbeats

The muscle weakness will create problems such as difficulty lifting objects, running or getting out of a low seat.

How quickly limb-girdle MD progresses depends on the specific type. Many types get worse slowly, but others can develop more rapidly.

Oculopharyngeal muscular dystrophy

In oculopharyngeal MD, symptoms are not usually apparent until a person is around 50 or 60 years old. It affects the muscles in the eyes (ocular) and the throat (pharyngeal).

Symptoms of oculopharyngeal MD can include:

• ptosis (droopy eyelids)
• dysphagia (difficulty swallowing)
• progressive restriction of eye movement as the eye muscles become affected
• limb weakness around the shoulders and hips

As the eyelids droop, they can cover the eyes and impair vision. It is also possible to develop double vision (diplopia).

The dysphagia can eventually make it hard to swallow solid foods, liquids and even small amounts of saliva. This can lead to chest infections if food and drink is accidentally swallowed the "wrong way" into the lungs. However, with treatment to manage the symptoms, a person's life expectancy is not usually altered.

Emery-Dreifuss muscular dystrophy

People with Emery-Dreifuss MD usually begin to develop symptoms during childhood or adolescence.

In the early stages, people with the condition usually develop muscle contractures. This is where muscles and tendons become shortened and tightened, limiting the range of movement at nearby joints.

Areas commonly affected by muscle contractures include the arms, neck and feet. This means that people with Emery-Dreifuss MD may have difficulty straightening their elbows or bending their neck forward, for example.

Like all types of MD, Emery-Dreifuss MD also causes progressive muscle weakness, usually beginning in the shoulders, upper arms and lower legs. This can make it hard to lift heavy objects or raise your arms above your head, and you may have an increased tendency to trip over things.

Later on, the hip and thigh muscles become weaker. This can make activities such as walking up stairs difficult. People with Emery-Dreifuss MD will often eventually require a wheelchair as they become unable to walk.

Emery-Dreifuss MD can also affect the electrical signals to the heart, causing heart block. This can cause people with the condition to develop an abnormally slow heartbeat and palpitations, which can lead to episodes of lightheadedness or fainting. The slow heartbeat can often be treated successfully with an implanted pacemaker.

Because of the risk of serious heart and respiratory problems, someone with Emery-Dreifuss MD will often have a shortened life expectancy. However, most people with the condition live until at least middle age.