Myositis

Myositis is the name for a group of rare conditions that can cause muscles to become weak, tired and painful. The word myositis simply means inflammation in muscles. If something is inflamed, it may be swollen. Myositis can affect people of any age, including children.

The main muscles to be affected are around the shoulders, hips and thighs. Having myositis can also lead to other parts of the body being affected, such as the skin, lungs or heart. Sometimes myositis can affect the muscles that carry out tasks such as breathing and swallowing. There are several types of myositis.

The two most common types:

• Polymyositis: ‘Poly’ means many. Polymyositis means that many muscles are affected by inflammation. This type doesn’t often affect other parts of the body much. Polymyositis is a chronic illness featuring progressive muscle weakness with periods of increased symptoms, called flares or relapses, and minimal or no symptoms, known as remissions.

• Dermatomyositis: ‘Derma’ means skin. Dermatomyositis causes similar symptoms in muscles, but there is also a skin rash. It's more common in women and can also affect children (juvenile dermatomyositis).

Polymyositis, dermatomyositis, as well as other types of myositis, are autoimmune conditions.

The immune system is the body’s natural self-defense system. When healthy, it protects us from infection, injury and illness. However, in people who have autoimmune conditions, the immune system gets confused and mistakenly attacks the body’s own healthy tissues.

Polymyositis and dermatomyositis are the two main types of myositis. Here are some of the others:

• Inclusion body myositis (IBM): Inclusion body myositis (IBM) causes weakness in muscles, usually near the ends of the arms or around the tops of the legs. This can make it difficult to grip objects, or can cause the knee to give way and lead to falls. This condition can also make swallowing difficult.

• Anti-synthetase syndrome: Anti-synthetase syndrome is a condition where several parts of the body are affected by inflammation. It can affect the muscles, and elsewhere, such as the lungs and skin. This lung condition can potentially be serious, which is why prompt medical treatment is important. Early symptoms can be a dry cough, which can occur before skin and muscle symptoms.

• Immune-mediated necrotizing myopathy: This type of myositis has been discovered more recently. It causes muscle cells to rapidly die in a process called necrosis. Weakness is usually very severe and people with this condition will often struggle to walk and use their arms. In extremely rare cases, this condition can be triggered by statin medication.

• Post-infectious reactive myositis: Infectious or post-infectious reactive myositis can occur during and after some viral infections. Even after the virus has gone, the immune system may cause inflammation in some parts of the body for a few months.

• Drug-induced myopathies: Drug-induced myopathies can sometimes appear like myositis. The most common drugs to cause this are statins used to lower people’s cholesterol levels. Usually, stopping this drug treatment leads to improvement in symptoms. Occasionally, the symptoms can last after the drug treatment has been stopped and people can develop myositis.

The symptoms of myositis vary between different people.

They can include:

• Weak and tired muscles that can make everyday tasks such as climbing stairs, brushing hair, and getting in and out of cars difficult

• Pain in muscles

• Muscles feeling tender to touch

• Muscles can sometimes swell

• Generally feeling unwell

• Weight loss

• Night sweats.

The most common muscles to be affected are around the shoulders, hips and thighs. The weakening and tiredness in the muscles can make people with myositis more likely to fall over.

With dermatomyositis you can have the above symptoms as well as:

• A red or pink rash on the upper eyelids, face and neck, and on the backs of the hands and fingers

• Swelling of the affected skin

• Puffiness and colouring around the eyes.

Some other medical conditions can appear similar to myositis. These include:

• The side effects of some medications – for example, steroids and drugs to lower your cholesterol levels, such as statins

• Effects of drinking too much alcohol over a long period • hormonal conditions – for example, underor overactive thyroid glands

• Low vitamin D levels

• Abnormal calcium or magnesium levels

• Infections

• Other rare muscle conditions – for example, where muscles waste away.

In most cases the pain and feelings of being unwell are eased with drugs. Even in severe cases most people with myositis eventually respond to treatment.

You may need to try more than one treatment before you find the right one for you.

Muscle strength can take longer to get back to normal. Once myositis is controlled with treatment, exercises can also help to improve muscle strength.

Although people can make a good recovery, some never regain their original muscle strength or function.

Sometimes, drug treatments don’t work fully and the muscles can remain weak. We are still doing research into why this is the case.

Occasionally, myositis can affect breathing and swallowing. This may occur at the start of severe cases when the muscles used for these important tasks become weak.

On rare occasions, this condition may cause weakening of the heart.

If there is inflammation in the lungs this can cause scarring, which can affect how the lungs work.

Lung and heart conditions can cause long-term breathlessness. For this reason, you may be referred to a heart or chest specialist if there’s a risk of these problems developing.

Children with dermatomyositis may develop painful deposits of the mineral calcium in damaged muscles. These deposits, combined with loss of mobility, can occasionally result in permanently rigid joints, which are called contractures.

Polymyositis occasionally occurs in patients who have other autoimmune conditions such as rheumatoid arthritis, lupus or systemic sclerosis (scleroderma).

On rare occasions, myositis can be associated with cancer. Most people with myositis don’t develop cancer, but your doctor might arrange tests such as a chest x-ray or an ultrasound scan of your abdomen and pelvis to be on the safe side.

There is no single test that can show for certain if someone has myositis.

Your doctor will talk to you about your symptoms and examine you. Because the symptoms of myositis are similar to many other conditions you’ll probably have blood tests and other examinations.

• Blood tests: There is no autoantibody test that can prove for certain you have myositis, but there are tests that can be helpful in making a diagnosis. One of these is the anti-nuclear antibody test (ANA). This is a test to see if your blood has antibodies that attack the central part of a cell called the nucleus.

• Electromyography: You may have a test called electromyography (EMG). This involves a tiny needle electrode, being inserted into the muscle to record electrical messages from nerve endings that enable your muscles to move. An unusual pattern of electrical activity in a number of different muscles can be due to myositis. The test isn’t very painful but may be uncomfortable.

• Muscle biopsy: A small sample of your muscle may be taken from one of your larger muscles, for example at the side of your thigh or calf, and examined under a microscope to look for signs of inflammation. This is called a biopsy. You’ll be given a local anaesthetic to numb the area while the sample is taken, but there may be some discomfort for a few days afterwards.

• Magnetic resonance imaging (MRI): An MRI scan can help work out where the inflammation is. Sometimes MRI scans can pick up areas of muscle that are being replaced by fat, indicating damage. An MRI is a scan that uses magnets to look at what is happening inside your body. It can show soft-tissue damage – in the muscles, ligaments or nerves – as well as any problems with the bones.

• Drugs: The first choice of treatment of myositis is steroids, which are usually given in high doses to begin with. Steroids can be given as tablets or injections. They should reduce the inflammation quickly, settle muscle pain and the feeling of being unwell.

• Exercise and physiotherapy: It’s probably best to rest when your myositis is very active, but once it has calmed down doing regular exercise can greatly improve your symptoms and overall health. Aerobic exercise, which makes you breathe more heavily and your heart beat faster, is especially important to help restore muscle strength and improve stamina. At first this should ideally be done under the supervision of a physiotherapist, who’ll give you a tailored programme. You should avoid very strenuous exercise.