What is myositis?

Myositis is the name for a group of rare conditions that can cause muscles to become weak, tired and painful. It can sometimes cause muscles to swell.

For most people symptoms will be mild and won’t last long. In rare cases, there can be some serious complications.

The word myositis simply means inflammation in muscles. If something is inflamed, it’s usually painful.

The main muscles to be affected are around the shoulders, hips and thighs. Sometimes myositis can affect the muscles that carry out tasks such as breathing and swallowing.

There are several types of myositis, and the two main types are polymyositis and dermatomyositis.

Polymyositis means that many muscles are affected. ‘Poly’ means many. Dermatomyositis causes similar symptoms in muscles, but there is also a skin rash. ‘Derma’ means skin. Both are autoimmune conditions.

The immune system protects us from illness and infection. However, in people who have autoimmune conditions, the immune system gets confused and mistakenly attacks the body’s own healthy tissues.

One of the important weapons in a healthy immune system is inflammation. For example, when we have a cut the body sends fluid to the affected area so that white blood cells can fight off any infection.

However, if someone has an autoimmune condition the body can create inflammation when there’s no infection to fight. The inflammation itself can then cause problems.


The symptoms of myositis vary between different people.

Most people will only have mild symptoms that don’t last long. These 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, and also:

  • 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.

Other types of myositis

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

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. The symptoms are similar to those of polymyositis, such as muscle pain and weakness.

Usually, the condition is mild and can settle without treatment. Rarely, some people who have HIV infection can develop long-term viral muscle infections.

Drug induced myopathies

Drug-induced myopathies can sometimes appear like myositis. The most common drugs involved are a group of drugs called statins that are used to lower people’s cholesterol levels.

Usually, stopping this drug treatment leads to improvement in symptoms. For some people however, the symptoms can last after the drug treatment has stopped and people can develop myositis.

Inclusion body myositis

Inclusion body myositis is a rare condition that causes muscle weakness, usually in muscles near the ends of the limbs, for example hands, forearms and calves.

Inclusion body myositis doesn’t respond to steroids or disease modifying anti-rheumatic drugs (DMARDS), that are usually used to treat polymyositis and dermatomyositis.

If you’re diagnosed with polymyositis and steroids aren’t working, you may need further tests to look more closely for inclusion body myositis. Currently, there are no effective treatment options for inclusion body myositis.

While inclusion body myositis rarely leads to muscle pain, it causes muscles to slowly but progressively weaken and waste. This normally happens over 10 to 15 years. This condition affects more men than women, and generally affects people over the age of 50.

How is myositis likely to affect me?

The prospects for people with myositis are generally good.

For most people, symptoms will be mild and won’t last long. In most cases the pain and feelings of being unwell are eased with drug treatment. Even in severe cases most myositis patients respond to treatment.

Quite often the symptoms of myositis go away completely.

Muscle strength can take longer to get back to normal. Once myositis is controlled with treatment, you’ll be given exercises to improve muscle strength.

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

Possible complications

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

Moderate exercise can help you recover muscle strength. Moderate exercise is when you’re breathing faster but you aren’t straining yourself.

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 is 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 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

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 that 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, known as the nucleus.

About 80–90% of people with polymyositis and dermatomyositis test positive for ANA, but 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 polymyositis and dermatomyositis.

There are now almost 20 different autoantibodies which can be present in people with myositis. Tests for these can 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.


You may have a test called electromyography (EMG). This involves a tiny needle electrode 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, and examined under a microscope. This is called a biopsy.

The site of the biopsy might be chosen using a magnetic resonance imaging (MRI) scan to assess the area. It’s most useful to have the biopsy at the part of the muscle that looks the most badly affected.

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.

The biopsy may reveal damage being caused to cells in the body that make your muscles contract, leading to muscle weakness and fatigue.

Sometimes, you may need to have another muscle biopsy if your condition doesn’t improve with standard treatments. This could be to check if you have inclusion body myositis.


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


The first choice for treatment of myositis is steroids, which are usually given in higher doses to begin with.

Steroids can be given as tablets or injections. They should reduce the inflammation very 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.

When taking steroid tablets you must carry a steroid card, stating your dose and how long you’ve been taking it. If you become ill or are involved in an accident in which you’re injured or become unconscious, it’s important for the steroids to be continued. The dose might need to be increased. Steroid treatment can prevent your body from producing enough natural steroids in response an injury. Your doctor, rheumatology nurse specialist or pharmacist can give you a steroid card.

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. Talk to your doctor about this.

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. Such drugs include methotrexate, azathioprine, ciclosporin and mycophenolate.

The drug cyclophosphamide can also be given as a drip into a vein, which is known as an intravenous infusion. This is usually done in a hospital.

These are all 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. A small number of people with severe muscle disease and complications have therefore been treated with biological therapies, which are newer types of disease modifying drugs.

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

A biological therapy occasionally used to treat myositis is rituximab.

In some severe cases, treatment with an immunoglobulin infusion is offered.

Immunoglobulins are antibodies collected from blood donations given by healthy people. They can help stop your immune system from attacking your own tissues. This treatment is usually given in hospital and it can be repeated if needed. Sometimes you might feel a little unwell, as if you have flu, during the infusion.

Even in severe cases, myositis usually responds well 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. Very strenuous exercise should be avoided.

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

Most people will recover completely from myositis. However, some people with severe symptoms never fully recover.

Even for people who do fully recover, it may take weeks or months for your body to repair your muscles and you may get tired more quickly than normal. Don’t worry if you’re not back to full strength straight away, continuing to exercise as regularly as you can will greatly help.

Research and new developments

Versus Arthritis has funded multiple research studies to further our understanding of myositis.

We’ve funded research to look at the link between genes people inherit, the presence of certain antibodies and the severity of their condition. This will allow doctors to predict which patients will experience mild or severe disease and why. This will help identify targets for future drug development.

We’ve also funded research to develop a standard protocol of assessing children with suspected juvenile dermatomyositis to improve diagnostic techniques, treatment and outcomes for young people. As these conditions are rare, research centres are joining forces to aid recruitment to clinical trials.

We are currently supporting several studies into juvenile dermatomyositis at our centre for adolescent rheumatology at Great Ormond Street Hospital, in London.

Such research includes a study looking at the role of a specific white blood cell, a B cell, in myositis. Blood samples will be taken from young people with juvenile dermatomyositis and a group without the condition. The information gathered will improve our knowledge of the condition and may help to develop new and more effective treatments in the future.

Jo’s story

Jo sat on a bench with her dog at her feet.

I used to work for a theatre company in London’s West End. Before work I’d swim and I often went out in the evenings. We were renovating our first home and I had boundless energy.

One morning I awoke with a swollen knee, soon followed by the other. I went to the GP who did tests. Being diagnosed with rheumatoid arthritis and told my right knee needed replacing aged 25 was a shock.

Arthritis spread to every joint. I could hardly walk or get dressed. My arms and legs were getting weak and I had a red rash and swelling everywhere.

One morning my tummy was swollen and stretch marks appeared. My boyfriend (now husband) called the GP for an emergency appointment. I was seen by two GPs and sent to A&E.

By now I looked like the Michelin Tyres character, and was covered head to toe in a red rash. My heart was failing and there was concern for my kidneys.

After a long wait on a trolley, I was admitted to a gynaecology ward – the only bed available! Doctors had no idea why I was so ill, then one evening a consultant said I had dermatomyositis.

I was placed on steroids and immune suppression drugs, and began to improve. I started physiotherapy and hydrotherapy and slowly regained mobility, but would never get back the same function and stamina as before.

Once out of hospital I had help from friends and family. My husband took me to the local pool and eventually I was able to swim in the style of an ironing board!

We got my hands and arms moving again by endless jigsaws puzzles.

Ten years post diagnosis we moved to Norfolk with a view to adopting. I then had my biggest improvement in health. I walked our three dogs daily and took up cycling.

I had 13 years of myositis remission, but then relapsed. My fatigue was so bad, after taking the boys to school I’d fall asleep at the breakfast table. The next thing I knew, the school secretary was calling to say I was late collecting the boys. It took two years to find the right combination of treatment.

I try to walk regularly, but am slow and breathless. Ralf our Cocker Spaniel is happy chasing squirrels and returning to check on me.

I was diagnosed before easy access to medical information. My first piece of information was from Laurence Olivier’s biography, as he had dermatomyositis. Later I was given a leaflet by Arthritis Research UK. It had details for Myositis UK. This led to contact with Irene, who with her husband, had set up a small charity after their daughter was diagnosed. I felt less alone. I wanted something positive to come from my health situation, so became a trustee for Myositis UK.

I have several milestones coming up, 20 years as a charity trustee, 25 years with dermatomyositis, reaching half century, not out.