There are many different types of muscular dystrophy (MD). All types cause muscle weakness, but the areas affected and the severity of the symptoms are different.
Duchenne muscular dystrophy
As a result of the way it's inherited (see causes of MD), Duchenne MD mostly affects boys. Girls can occasionally be affected, although the condition tends to be milder.
Children with Duchenne MD usually start to have noticeable symptoms between 1 and 3 years of age. 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're 12 years old, as their muscles weaken and they lose the ability to walk. They can also develop scoliosis, where the spine begins to curve sideways. This can lead to one shoulder or hip being higher than the other.
By their mid-teens, some people with Duchenne MD will develop dilated cardiomyopathy. This condition affects the heart muscles, causing the heart's chambers to enlarge and the walls to get thinner.
By their late-teens or early 20s, people with Duchenne MD may start to have breathing problems. The condition can also affect the intercostal muscles (muscle tissue between the ribs) and the diaphragm (the large, thin sheet of muscle between the chest and abdomen).
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.
As with other types of muscular dystrophy, myotonic dystrophy involves progressive muscle weakness and muscle wasting. However, it's 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
- difficulty swallowing
- behavioural and learning problems in children
- a slow and irregular heartbeat (cardiac arrhythmia)
Myotonic dystrophy is highly variable and often gets worse very slowly, with little change over long periods of time. However, it can become more severe as it's passed down through the generations.
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's a risk of the electrical impulses that control the heartbeat travelling 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 (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.
If you have myotonic dystrophy, it's important that you're well informed about your condition, and that you tell any healthcare professionals you see that you have it. Myotonic dystrophy can cause 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 1 in 3 people with facioscapulohumeral MD are unaware of any symptoms until well into adulthood. Others develop problems in early childhood. The condition tends to progress slowly.
Signs in your child may include:
- sleeping with their eyes slightly open
- an inability to squeeze their eyes tightly shut
- an inability to 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
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 doesn't 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're 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 sports at school
During late childhood or early adulthood, people with Becker MD often find they have difficulty running, walking quickly and climbing stairs. As they get older, they may also find lifting objects above waist height difficult.
Most people with Becker MD will be able to walk into their 40s and 50s but often find they need to use a wheelchair as their condition progresses.
If you have Becker MD, you're also at risk of developing dilated cardiomyopathy and breathing problems. However, Becker MD progresses at a slower rate than Duchenne MD, and those with the condition often have a normal lifespan.
Limb-girdle muscular dystrophy
Limb-girdle MD refers 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. Males and females are equally affected.
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, whereas others can develop more rapidly.
Oculopharyngeal muscular dystrophy
In oculopharyngeal MD, symptoms aren't usually apparent until a person is around 50 years old. It affects the muscles in the eyes (ocular) and the throat (pharyngeal).
Symptoms of oculopharyngeal MD can include:
- droopy eyelids
- difficulty swallowing (dysphagia)
- 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's also possible to develop double vision.
Dysphagia can eventually make it difficult 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 isn't usually altered.
Emery-Dreifuss muscular dystrophy
People with Emery-Dreifuss MD often begin to develop symptoms during childhood or adolescence.
In the early stages, people with the condition usually develop muscle contractures (where the 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 difficult 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, making 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 heart's electrical signals, causing heart block. This can result in people with the condition developing 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.
Due to 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.