If you’ve noticed that you’re now having trouble lifting a gallon of milk from the fridge or getting up out of a chair, you may just chalk it up to a sign of getting older. But sometimes this weakness in your everyday activities could be the first symptom of myositis, a rare condition that affects between 50,000 and 75,000 people in the U.S., many of them women.
Myositis is an umbrella term for related types of autoimmune conditions known as idiopathic inflammatory myopathy (IIM) that all have one thing in common: a weakness in the muscles you use to move your body.
The forms of myositis are:
- Polymyositis (PM)
- Dermatomyositis (DM)
- Immune-mediated necrotizing myopathy (IMNM)
- Inclusion body myositis (IBM)
- Juvenile forms of myositis (JM), which affect children and teens
- Antisynthetase Syndrome (ASyS)
Myositis can be difficult to diagnose and to treat — and it’s not curable. But you can manage your symptoms and perhaps even get the disease under remission with the right medications and treatment plan. The exception is inclusion body myositis, as there is yet no treatment available for this form of myositis.
Symptoms of Myositis
“Myositis is variable for every person. Generally, the symptoms are muscle weakness, sometimes pain, and often extreme fatigue,” says Linda Kobert, RN, MSN, the research and communications director of the Myositis Association in Alexandria, Virginia. “But the muscle weakness can appear in different ways in different forms.”
While all types of myositis cause muscle weakness, where and how that weakness shows up can differ depending on your subtype.
Polymyositis (PM) and Dermatomyositis (DM): Both polymyositis and dermatomyositis typically cause weakness in the muscles closest to the center of your body — like your thighs, hips, and shoulders — and usually affect both sides equally. This might make everyday tasks harder, like climbing stairs, washing your hair, or getting in and out of the car. Some people also experience difficulty swallowing, which can make eating and drinking uncomfortable or even unsafe.
Dermatomyositis (DM): In addition to muscle weakness, dermatomyositis also causes a blotchy, discolored rash that can appear on your face, eyelids, chest, shoulders, and the back of your neck. The rash can be itchy and painful.
Immune-Mediated Necrotizing Myopathy (IMNM): Like polymyositis and dermatomyositis, IMNM causes weakness in the muscles closest to the center of your body. However, IMNM tends to come on more quickly and can cause more severe weakness than other subtypes. Some people with IMNM also have difficulty swallowing.
Inclusion Body Myositis (IBM): Inclusion body myositis also affects the shoulders and upper legs, but it can additionally cause weakness in the hands and fingers — making it hard to grip objects, button a shirt, or open a jar. Unlike the other subtypes, IBM often affects one side of the body more than the other. Swallowing difficulties are also common in IBM and can worsen as the condition progresses.
Causes of Myositis
No one knows for sure what triggers myositis. “Researchers believe that some people may have a genetic predisposition for developing some form of autoimmune disease,” says Kobert. One family member may develop myositis, for example; another member may develop such other autoimmune diseases as lupus or multiple sclerosis. The exception is inclusion body myositis. There’s a debate among researchers whether IBM is an autoimmune disorder or a neurodegenerative one.
Like many other autoimmune rheumatologic diseases, women between the ages of 30 and 60 are mostly affected. The exception: juvenile forms of myositis, as well as sporadic inclusion body myositis (sIBM), which typically affects men after the age of 50, says Rohit Aggarwal, MD, a rheumatologist, professor and Medical Director, Rheumatology at the University of Pittsburgh School of Medicine as well as the past-chair of the medical advisory board for the Myositis Association.
There are other factors that may play a role. Very rarely, people taking statins can develop myositis, says Dr. Aggarwal, who cautions that the risk is very low and the benefits of statins far outweighs the odds of developing the disease. Most of the time, when patients stop taking statins, the myositis resolves in three to six months, he explains, but a small subset go on to develop the autoimmune form known as necrotizing myopathy. “These patients often need long-term treatment,” he adds.
Where you live may also affect your chances of developing dermatomyositis. “In countries or regions where there’s more exposure to U.V. (Ultraviolet) radiation, there are higher incidents of dermatomyositis,” says Dr. Aggarwal. But again, he cautions, you probably need to have a genetic predisposition along with increased sun exposure, as well as other environmental triggers, to get dermatomyositis.
Myositis vs. Similar Conditions
Myositis can be tricky to diagnose when patients come to their primary providers complaining of muscle weakness, fatigue, and rashes. For one, myositis is rare and doctors may not have had any experience diagnosing or treating it, or even know much about the disease. For another, the symptoms of myositis are common to many types of autoimmune or inflammatory diseases.
Dermatomyositis rash can be mistaken for the rash that accompanies lupus or even psoriasis. Other forms of myositis can be misdiagnosed as fibromyalgia. IBM is sometimes mistaken for amyotrophic lateral sclerosis (ALS), or Lou Gehrig’s disease, says Kobert.
One way myositis differs from fibromyalgia: “I teach physicians that myositis, in most cases, is muscle weakness much more than muscle pain. Typically, in fibromyalgia, there is no objective muscle strength problems — the muscles are painful and tender, but they’re not weak upon examination,” says Dr. Aggarwal, who is also the medical director of the Arthritis and Autoimmunity Center at the University of Pittsburgh’s Medical School.
To avoid misdiagnosis, you need a savvy primary care doctor or a specialist, typically a rheumatologist, neurologist, or, in the case of dermatomyositis, a dermatologist.
How Myositis Is Diagnosed
“Dermatomyositis is probably easier to diagnose than other forms of myositis, because of the characteristic rashes,” says Dr. Aggarwal. Patients are usually referred to a dermatologist, who can recognize these specific rashes and then perform a skin biopsy to reach a conclusive diagnosis, he adds, though a wrong diagnosis can still occur.
Other criteria that can clue a specialist that you might have myositis include physical exam to see if you have proximal muscle weakness — usually those muscles closest to the trunk of your body — as well a blood test to discover if a muscle enzyme called creatine kinase (CK) is elevated. People with myositis usually have very high levels of CK. And nearly three-quarters of patients may have one of the 15 to 17 myositis-specific autoantibodies, or abnormal proteins that signal an autoimmune disorder, says Kobert. These autoantibodies can also indicate information about your prognosis as well as your risk of developing an associated condition, such as interstitial lung disease or cancer, notes Dr. Aggarwal.
Other diagnostic tests, like an electromyogram (EMG) and nerve conduction velocity (NCV) studies, can differentiate muscle problems (called myopathies) from neurological problems, like myasthenia gravis, he explains. Sometimes MRIs are used to spot muscle inflammation or damage, which can then help the doctor to decide which muscle tissue to biopsy.
“The biopsy can reveal inflammation, either within the bundles of muscle fibers, which is a sign of polymyositis or IBM, or around the bundles of muscle fibers, which is sign of dermatomyositis,” says Dr. Aggarwal. “If you have three or four positive results among all those tests, then generally that leads to a myositis diagnosis.”
How Myositis Is Treated
Currently, there’s no FDA-approved treatment specifically for any type of myositis. Steroids like prednisone are often the first-line treatment for for polymyositis, dermatomyositis, necrotizing myopathy, and juvenile myositis. Steroids can slow down inflammation and improve muscle strength quickly. (There is no medical treatment for IBM, though there are clinical trials.)
The trouble with steroids is that people with myositis have to take very high doses for a long time. “You’re talking about 60 to 80 milligrams of steroid tapered over six to twelve months. That leads to significant side effects, including bone and muscle-mass loss, diabetes, mood changes, and effects on cholesterol and the heart,” says Dr. Aggarwal. “That’s why we try to limit steroids as much as we can.”
Along with steroids or, sometimes instead of them, people with PM, DM, IMNM, and NM may also take an immunosuppressant drug, such as methotrexate, azathioprine, mycophenolate mofetil, cyclosporine, tacrolimus, cyclophosphamide, or hydroxychloroquine, among others, to inhibit the immune system. These drugs come with their own side effects (such as nausea, headaches, and effects on liver function), and they may lower your resistance to infections.
For people whose myositis doesn’t respond well to standard treatments, doctors may prescribe biologic medications off-label — meaning the drug is used for a condition other than the one it was FDA-approved to treat.
IVIg (intravenous immunoglobulin) has been FDA-approved for adults with dermatomyositis — meaning it has gone through rigorous testing and met the FDA’s standards for treating this condition. IVIg is also used off-label across other myositis subtypes. New treatments are currently being studied in clinical trials, adding hope for additional biologic treatments for other forms of myositis.
Treatment Doesn’t Stop at Medication
“The goal here is to make the disease go into remission or get to minimal disease activity, which means minimal rash or muscle weakness or pain that can be controlled with medications. For the patients who do get better, they are able to go back to about 90 percent of their baseline,” explains Dr. Aggarwal. Complete remission is rare, he notes — only about 10 to 20 percent of patients experience that (your autoantibodies can reveal if you’ll be among them).
“For those not helped by medication, myositis worsens over time and then eventually plateaus,” says Dr. Aggarwal. Patients may need to use a wheelchair or walker or significant help to get around, not to mention have difficulty in doing daily activities.
There is one thing you can keep doing, though, no matter what your prognosis.
“Exercise can help all forms of myositis, although what form of exercise depends on your individual needs,” says Kobert. This is especially true of IBM, as exercise can help decrease the rate of the disease’s progression. While a physical therapist or rehab specialist can help you create a specific workout, the best one for you may be the one that you can incorporate into your daily routine, be it water exercise, yoga, or walking. The key is knowing your limits and not pushing yourself to the point of exhaustion.
Keep Reading
Campanilho-Marques, R., Fonseca, J. E., & Machado, P. M. (2025). Treatment of idiopathic inflammatory myopathies. Joint Bone Spine, 92(6), 105932. doi: https://doi.org/10.1016/j.jbspin.2025.105932
Nagy S, Khan A, Machado PM, Houlden H. Inclusion body myositis: from genetics to clinical trials. J Neurol. 2023 Mar;270(3):1787-1797. doi: https://doi.org/10.1007/s00415-022-11459-3.
