Myositis

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

Blood tests can look for:

signs of damaged muscles

inflammation levels within the body

the presence of autoantibodies, which are tiny proteins that can attack the body’s own healthy tissues and cells.

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.

Healthy people can also test positive so it’s only helpful alongside all the other information about your symptoms.

Other autoantibody tests include ENA (extractable nuclear antigens) and the anti-Jo-1 test. These tests are sometimes positive in people with myositis.

There are now lots of different autoantibodies which can be present in people with myositis. Tests for these can sometimes be useful for predicting your responses to treatment.

Even if these tests haven’t led to a diagnosis of myositis, they may have helped your doctor rule out other conditions. There are other tests to help confirm a myositis diagnosis.

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.

Sometimes, you may need to have another muscle biopsy if your condition doesn’t improve with standard treatments. This is to check for the proteins found in inclusion body myositis.

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.

Treatment for myositis includes a combination of drug treatment and exercise.

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.

High doses of steroids can have side effects, so your doctor will reduce the dosage as quickly as possible.

Taking steroids over a long time can increase the risk of developing the condition osteoporosis, which causes bones to become thin and fracture more easily. There are drugs you can take alongside steroids to reduce the risk of developing osteoporosis. This includes bisphosphonates, which can slow bone loss.

Sometimes the symptoms of myositis can flare up when the steroid dose is lowered and your doctor may often prescribe other drugs to help reduce the inflammation. These include methotrexate, azathioprine, ciclosporin, tacrolimus and mycophenolate.

Most of these are types of disease-modifying anti-rheumatic drugs (DMARDs), and you will need regular blood tests to check for possible side effects.

Occasionally these drugs aren’t able to control myositis. In these more severe cases, the following drugs might be available:

the DMARD cyclophosphamide

the biological therapy rituximab

immunoglobulin.

Biological therapies work by blocking specific targets within the immune system that cause inflammation.

Immunoglobulins are antibodies collected from blood donations given by healthy people, which can help stop your immune system from attacking your own tissues. This treatment is usually given as a drip into a vein in your arm, known as an intravenous drip. This will be carried out in hospital and it can be repeated if needed. Sometimes you might feel a little unwell, during the treatment itself.

Even in severe cases, myositis usually responds to treatment, although many people need life-long drug treatment to keep their condition under control.

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.

Children with juvenile dermatomyositis will need more vigorous physiotherapy to reduce the risk of joints, especially the knees, becoming permanently bent.

People with myositis can make a good recovery. However, some people with severe symptoms may never fully recover.