Myositis: Symptoms, Types, Treatment and Recovery

Myositis means inflammation of the muscles. It makes muscles weak, and sometimes sore. A short bout can follow a virus such as the flu. The long-term forms happen when the immune system attacks the muscles by mistake. These need treatment, and early treatment helps protect strength.

Key points

The main sign of the long-term forms is weakness in the hips, thighs, shoulders and neck. Climbing stairs or getting out of a chair becomes hard.
Some types also affect the skin, lungs or swallowing.
Blood tests, an MRI and often a small muscle sample (biopsy) confirm the diagnosis.
Steroids and other medicines that calm the immune system treat most types. Exercise and physical therapy help too.
Dark brown urine with muscle pain or weakness needs urgent care.

Types and causes of myositis

Autoimmune myositis

In these conditions, the body’s defense system turns on its own muscle. Doctors call the group inflammatory myopathies. They are rare.

Dermatomyositis causes muscle weakness plus a rash. The rash may be purple-red on the eyelids, or appear as red, scaly bumps over the knuckles, elbows or knees. It can also show on the chest, upper back and shoulders. It can affect children as well as adults. In adults, it is sometimes linked to a hidden cancer.
Polymyositis causes weakness without a rash.
Immune-mediated necrotizing myopathy can cause fast, severe weakness. Some cases are triggered by statin cholesterol medicines, even after years of use, and the weakness keeps going after the statin is stopped.
Overlap myositis comes with another autoimmune disease, such as lupus, scleroderma or mixed connective tissue disease.
Antisynthetase syndrome combines myositis with lung scarring, joint pain, and thick, cracked skin on the fingers.
Inclusion body myositis mostly affects people over 50, more often men. It slowly weakens the thigh muscles and the muscles that bend the fingers, and it can cause trouble swallowing. Unlike the other types, it doesn’t respond well to immune treatment.

Short-term myositis

Viral infections. After the flu, COVID-19 or other viruses, muscles can become sore and weak. Children may get sudden calf pain and walk on their toes or refuse to walk. Adults more often have aching, tender muscles in the legs, back or arms. A yearly flu shot lowers the chance.
Parasites. Trichinosis, caught from undercooked pork or wild game such as bear, causes muscle pain, fever and puffy eyelids. Cooking meat all the way through prevents it.
Medicines. Statins commonly cause mild muscle aches, which are different from true myositis. Some cancer immunotherapy drugs can also cause myositis.
Muscle breakdown (rhabdomyolysis). Very hard exercise, heat, crush injuries, some drugs and severe infections can damage muscle quickly. The released muscle protein can harm the kidneys.

Myositis symptoms

Weakness in the muscles closest to the trunk. You may struggle to climb stairs, rise from a chair or the toilet, lift your arms to brush your hair, or raise your head from a pillow.
Tiredness
Muscle aches or tenderness, though many people have little pain
Trouble swallowing, or choking on food or drink
Shortness of breath or a dry cough, if the lungs are involved
Rash, in dermatomyositis
Joint pain, fever or weight loss

The weakness usually develops over weeks to months, and on both sides of the body. Inclusion body myositis develops more slowly, over years.

How it’s diagnosed

Exam. The doctor tests the strength of different muscles and checks your skin.
Blood tests. Creatine kinase (CK) is a muscle enzyme that leaks into the blood when muscle is damaged. Antibody tests can point to a specific type of myositis and its likely course.
MRI. This shows which muscles are inflamed and helps choose the best spot for a biopsy.
Nerve and muscle test (EMG). A thin needle electrode records the muscles’ electrical activity.
Muscle or skin biopsy. A small piece of tissue is checked under a microscope. This is often the key test.
Lung and heart tests. A chest CT scan, breathing tests and an ECG check for spread beyond the muscles.
Cancer screening is advised for adults with dermatomyositis and some other types.

Myositis treatment

Autoimmune myositis usually needs long-term treatment. Care is often shared by a rheumatologist or neurologist, a physical therapist and other specialists.

Steroids. Prednisone or a similar medicine is usually the first treatment. The dose is slowly lowered once strength improves, to limit side effects such as weight gain, high blood sugar and bone thinning.
Steroid-sparing medicines. Methotrexate, azathioprine or mycophenolate are often added so less steroid is needed.
IVIG. Antibodies pooled from donated blood are given through a vein. It is approved for dermatomyositis and helps in other types too.
Other medicines. Rituximab, tacrolimus and other drugs are used for hard-to-treat cases or for lung disease.
Skin care. Sun protection, creams and hydroxychloroquine help the dermatomyositis rash. Sunlight can make it worse.
Exercise and therapy. A tailored exercise program is safe and helps rebuild strength and stamina. A speech therapist can help with swallowing.

For inclusion body myositis, there is no proven drug yet. Physical therapy, walking aids and help with swallowing keep people active and safe.

If a statin is behind muscle symptoms, your doctor may stop it or switch to a different cholesterol medicine.

RELATED REPORTS

Dazukibart is effective in reducing disease activity in adults with refractory dermatomyositis

Intravenous immune globulin improved disease severity in dermatomyositis

Living with myositis

Stay as active as your care team advises, and pace yourself on tired days.
Take steroids exactly as prescribed. Don’t stop suddenly.
Ask about calcium, vitamin D and bone protection while on steroids.
Get recommended vaccines, since treatment can weaken your defenses against infection. Ask before getting any live vaccine.
Many people regain much of their strength with treatment, though some have flares or lasting weakness.

When to see a doctor

Weakness that makes stairs, chairs or lifting harder over weeks
A new rash on the eyelids or knuckles along with weakness
New muscle weakness while taking a statin
A child with calf pain who won’t walk after an illness

Get emergency care for dark brown or tea-colored urine, severe weakness, trouble breathing or trouble swallowing.

Common questions about myositis

How long does myositis last?

It depends on the type. Viral myositis, such as after the flu, usually goes away by itself within a few days to two weeks. Autoimmune myositis lasts much longer and often needs treatment for years, though symptoms settle for long stretches in many people.

How is viral myositis treated?

Rest, fluids and pain relievers such as acetaminophen are usually enough, and the muscles recover as the virus clears. Ask before taking ibuprofen if you have kidney problems. See a doctor right away for dark urine, severe weakness, or a child who can’t or won’t walk.

Is myositis dangerous?

Viral myositis is usually mild. Autoimmune myositis is serious but treatable, and many people regain much of their strength and live for many years. The main dangers come from lung disease, trouble swallowing, heart problems or a cancer linked to dermatomyositis, which is why doctors check for them.

Is myositis painful?

It can be, but in autoimmune myositis weakness is usually a bigger problem than pain. Viral myositis tends to cause sore, tender muscles, often in the calves or thighs. Severe muscle pain with swelling or dark urine can mean muscle breakdown and needs urgent care.