Muscle Disease

What is muscle disease?

Muscle disease, also called myopathy, is the general term for conditions that damage or weaken the skeletal muscles you use to move. Some types are present from birth or run in families, while others develop later in life because of an illness, an infection or a medicine.

What symptoms does muscle disease cause?

Muscle weakness is the main sign of most muscle diseases, usually affecting your shoulders, upper arms, hips and thighs rather than your hands or feet. Symptoms can stay the same for years or slowly get worse, and in some conditions weakness comes and goes.

• weakness in your shoulders, upper arms, hips or thighs
• cramps, stiffness or spasms in your muscles
• feeling unusually tired or short of breath during activity
• difficulty with everyday tasks such as washing, dressing or brushing your hair
• struggling to rise from a low seat, climb a flight of stairs, or lift things above shoulder height
• falling more often than you used to
• aching or painful joints.

In children, muscle disease can show up as being slower to crawl or walk, floppiness as a baby, or struggling to keep up with friends during sport and play. Some types also affect the muscles used for swallowing or speech, which can cause choking or slurred words.

What causes muscle disease, and who is at risk?

Muscle disease falls into two broad groups. Some types are genetic: you inherit an altered gene from a parent, or are born with one even if neither parent has the condition. Others are acquired, meaning they develop later in life because of a separate illness, an infection, a hormone problem, or exposure to certain medicines or toxins.

Certain factors make some forms more likely. If a genetic form runs in your family, you have a higher chance of carrying the same gene fault, and a test can check for this. A few genetic types sit on the sex chromosomes, so they show up more often in men, though most affect men and women equally. Having any of the underlying conditions above, or taking certain medicines, raises your risk of the acquired forms in the same way.

How common a muscle disease is depends heavily on its type:

• inflammatory forms affect between nine and 32 people in every 100,000, and tend to be more common in women
• duchenne and becker muscular dystrophy, the most common inherited types, affect around 7 in every 100,000 people worldwide
• conditions caused by faulty mitochondria (the tiny structures inside your cells that generate energy) affect around 1 in 5,000 people
• muscle symptoms linked to thyroid problems are common too: as many as 79% of people with an underactive thyroid notice some muscle symptoms, though a smaller number go on to have a diagnosable myopathy.

What types of muscle disease are there?

Doctors often group muscle diseases by whether they're inherited or develop later in life.

Muscle diseases you're born with:

• Congenital myopathy: weakness that's usually noticeable from birth or early childhood and often doesn't get worse over time, affecting muscles all over the body rather than just those closest to your trunk.
• Mitochondrial myopathy: caused by a fault in the tiny structures inside your cells that generate energy, which can also affect your heart, brain or digestive system alongside your muscles.
• Metabolic myopathy: caused by a missing or faulty enzyme your muscles need to work properly, often causing pain and poor stamina during exercise.
• Muscular dystrophy: a group of conditions where muscle tissue gradually breaks down, mainly affecting the arms and legs and sometimes the face or eyes.

Muscle diseases that develop later in life:

• Autoimmune or inflammatory myopathy: your immune system mistakenly attacks your own muscles.
• Toxic myopathy: caused by a medicine or toxin, such as alcohol, statins, steroids or certain HIV treatments.
• Endocrine myopathy: caused by a hormone imbalance, most often an underactive or overactive thyroid.
• Infectious myopathy: caused by an infection, such as flu, Lyme disease or certain parasites.
• Electrolyte-related myopathy: caused by abnormal salt levels in your blood, such as potassium or magnesium.
• Critical illness myopathy: develops during a stay in intensive care, often linked to being immobile for a long period or to some of the medicines used there.

How is muscle disease diagnosed?

Your GP is a good first point of contact if you're concerned about your symptoms. If they suspect a muscle disease, they can arrange for you to see either a neurologist or a rheumatologist.

That appointment usually starts with questions about your own health, your family's health and any medicines you take, followed by a physical check of your balance, reflexes, muscle strength, skin and sense of touch.

• blood tests, to check muscle enzymes, salt levels, hormone levels, or signs of an autoimmune condition
• a genetic test, to look for an altered gene
• a test called electromyography, or EMG, often combined with nerve conduction studies, to check how well your muscles and nerves are working electrically
• an MRI scan of your muscles
• a muscle biopsy, taking a tiny sample of muscle to examine closely under a microscope.

If muscle disease runs in your family and you're expecting, or hoping to conceive, your GP can put you in touch with a genetic counsellor. They can explain the tests available at different stages of pregnancy, including a blood test, CVS or amniocentesis.

How is muscle disease treated?

Your care team will build a treatment plan around the type of muscle disease you have and your specific symptoms. Most people are supported by more than one specialist, and many acquired forms can be well controlled once treatment starts.

Non-surgical treatment

• physiotherapy and regular exercise, to help maintain movement and ease pain
• occupational therapy, to help you manage daily tasks safely
• medicines that calm an overactive immune system, such as corticosteroids or immunosuppressants, for autoimmune and inflammatory types
• stopping or changing the medicine responsible, for toxic myopathy, only ever under medical guidance
• antibiotics or other treatment for the underlying infection, for infectious myopathy
• specific medicines for a small number of inherited types, such as Duchenne muscular dystrophy or Pompe disease, alongside ongoing research into gene therapy
• mobility equipment, such as walking aids or a wheelchair, as weakness progresses.

Surgical treatment

Surgery isn't a routine part of treating most muscle diseases, but your care team may recommend it for specific complications. For some inherited types such as muscular dystrophy, this can include surgery to manage scoliosis or tight joints, or a pacemaker if the condition has affected your heart rhythm.

When should I see a doctor?

• muscle weakness, pain or stiffness in you or your child isn't easing off
• your child seems slower than expected to crawl, walk or reach other physical milestones
• symptoms that were manageable start getting worse or interfering with daily life
• you or your partner are expecting, or hoping to have children, and muscle disease runs in either of your families.