Myositis
Medically reviewed by Dr Ramani Arumugam, Consultant Rheumatologist ·
If climbing stairs, getting up from a chair or lifting your arms to wash your hair has slowly become hard work, your muscles may be telling you something. Myositis is inflammation inside the muscles, and it usually shows as weakness more than pain. It is rare, it is often missed, and it responds best when treatment starts early.
Myositis: understanding the condition
This one-page summary brings together the main types, the symptoms, the tests and the treatment options. Tap the image to open it full size if the print is small on your phone.
View the full-size infographicUnderstanding myositis
Myositis means inflammation of the muscles. Doctors also call this group of conditions the idiopathic inflammatory myopathies. The immune system, which normally protects you from infection, starts to attack your own muscle tissue. The muscles closest to the centre of the body are affected most: the shoulders, upper arms, hips and thighs. Myositis can also involve the skin, joints, lungs, heart and the muscles used for swallowing. That is why I look at the whole person and not only the muscles.
The main types of myositis
- Dermatomyositis. Muscle weakness together with a typical skin rash on the eyelids, knuckles, chest or shoulders.
- Antisynthetase syndrome. Muscle, lung and joint inflammation linked to a specific group of antibodies, most often anti-Jo-1.
- Polymyositis. Muscle weakness without the skin changes.
- Immune-mediated necrotising myopathy. Weakness that is often more severe and comes on faster. A rare form is linked to statin (cholesterol) medicines.
- Inclusion body myositis. Slower weakness in older adults, often in the thighs, hands and feet. It does not usually improve with immune-suppressing medicines.
- Overlap myositis. Myositis in someone who also has another connective tissue disease, such as lupus or systemic sclerosis.
Why it happens
We do not yet know the exact cause. Myositis is an autoimmune condition. It seems to develop in people with certain genes after a trigger, and possible triggers include viral infections, certain medicines and, in some adults, cancer. It most often starts in adults aged 40 to 60 and in children aged 5 to 15, and it affects women more often than men. It is not contagious, and it is not caused by anything you did.
How I reach the diagnosis
No single test confirms myositis. I put several pieces together.
- Your story and examination. Which muscles are weak, how fast it came on, and whether there is a rash, joint pain, breathlessness or trouble swallowing.
- Blood tests. Muscle enzymes such as creatine kinase (CK) leak into the blood when muscle is damaged. I also check ANA and a myositis antibody panel. The antibody result often points to the type of myositis and the organs I need to watch.
- Muscle MRI. This shows inflammation across a large area of muscle and helps choose a biopsy site if one is needed.
- Electromyography (EMG). This measures the electrical activity of the muscle.
- Muscle biopsy. In some patients a small sample of muscle confirms the type and rules out other muscle diseases.
- Lungs and swallowing. A chest scan and lung function tests if the lungs may be involved, and a swallowing assessment if food is sticking.
- Cancer screening. In adults, guided by your age and the type of myositis.
I also look for conditions that can look similar, such as thyroid problems, side effects of medicines and inherited muscle conditions.
What treatment looks like
The aim is to switch off the inflammation, bring back strength and protect the lungs and other organs.
- Corticosteroids. Usually the first treatment. I start at a dose that controls the inflammation, then reduce it slowly as your strength and blood tests improve. Severe disease may need steroids through a drip.
- Steroid-sparing medicines. Methotrexate, azathioprine, mycophenolate or tacrolimus let me lower the steroid dose and limit its side effects.
- IV immunoglobulin (IVIG) and rituximab. Options when the disease is severe or has not responded.
- Monitoring. I follow your muscle enzymes and test your strength at each visit. Strength often starts to return over the first 6 to 12 weeks.
- Protecting the rest of you. Long-term steroids affect bone, so I plan bone protection early. I also review your vaccinations because treatment lowers your defences against infection.
- Physiotherapy. Rest when inflammation is at its worst, then a guided exercise plan to rebuild strength safely.
What you can do yourself
- Take your medicines as prescribed. Never stop steroids suddenly.
- Keep moving with a plan from a physiotherapist, and pace yourself on good days.
- Tell me early about new breathlessness, a cough that does not clear, or food sticking when you swallow.
- Bring a list of every medicine and supplement you take, including cholesterol tablets.
- Look after your bones with enough calcium and vitamin D, and check your falls risk if your legs feel weak.
What the future holds
The outlook depends on the type of myositis and which organs are involved. Most types respond to treatment, and many people regain useful strength and return to their usual activities. Some people need a low dose of medicine for the long term, and symptoms can flare if treatment is reduced too quickly. Regular follow-up lets me catch a flare, or a lung problem, early.
Some of the information on this page is adapted from the Merck Manual: Idiopathic Inflammatory Myopathies and The Myositis Association. It is general education and does not replace an individual medical assessment.
What myositis is
Myositis is a group of rare autoimmune conditions in which the immune system inflames the muscles. The main symptom is weakness in the shoulders, upper arms, hips and thighs that builds over weeks to months. Some types also affect the skin, joints, lungs and swallowing.
Symptoms to look out for
Difficulty climbing stairs or getting up from a low chair, the toilet or the floor
Difficulty lifting your arms above your shoulders, for example to comb your hair or hang clothes
Weakness on both sides of the body that slowly gets worse over weeks or months
Trouble lifting your head from the pillow
Difficulty swallowing, or food coming back up
Shortness of breath or a dry cough
Joint pain or swelling
Tiredness, fever or weight loss
Fingers that turn white or blue in the cold (Raynaud's)
A new rash on the eyelids, knuckles, chest or shoulders
Why this matters to a rheumatologist
Myositis is rare, so the early signs are often put down to age, tiredness or a medicine side effect. My job is to confirm that the muscle is inflamed, work out which type you have, and check the lungs, heart and swallowing. In adults I also look for a cancer that can sit behind some types. The type matters, because the treatment and the risks are different for each one.
Signs I would like you to seek care for
For emergency symptoms please seek urgent or emergency care first rather than waiting for a WhatsApp reply.
Difficulty swallowing, or choking on food or drink
New or worsening breathlessness
Weakness that is getting worse quickly over days
Muscle weakness together with a new rash
Muscle weakness or a high CK result while taking a statin, especially if it continues after the statin is stopped
Chest pain or palpitations
What a specialist review looks like
I ask how the weakness started and what you can no longer do easily. I test your strength muscle by muscle and examine your skin, joints and chest. I review any blood tests you already have and arrange the antibody panel, scans and other tests that are needed. Where it helps, I work with a neurologist, respiratory physician, dermatologist and physiotherapist. Then I explain the result in plain language and we agree a treatment and monitoring plan.
Questions my patients often ask me
Ordinary aches hurt but the muscle still works. In myositis the main problem is weakness: stairs, chairs and lifting your arms become difficult, often with little pain. Weakness that builds over weeks should be checked.
Speak with me
If stairs, chairs or lifting your arms have become harder, or a blood test has shown a high CK, WhatsApp my clinic. We can help you decide whether a rheumatology review is the right next step.
Other conditions I treat
This page is for general education only and does not replace medical advice. Please consult a qualified healthcare professional for diagnosis and treatment.