Myositis

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 five 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)
  • Necrotizing myopathy (NM)
  • Inclusion body myositis (IBM)
  • Juvenile forms of myositis (JM), which affect children and teens

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.”

If you have polymyositis or dermatomyositis, you typically have weak proximal muscles — the muscles that are closest to your body, such as the ones in your thighs or shoulders — equally on both sides. That might mean it can be hard for you to go up the stairs, wash your hair, or get in and out of the car.

If you have inclusion body myositis, you may also have weak shoulders and upper legs, but you might also find your fingers are so weak that it’s hard to grasp things.

People with dermatomyositis also have a blotchy rash along their face, chest, shoulders, and back of the neck that can be itchy and painful.

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 and an associate professor in at the University of Pittsburgh School of Medicine as well as the 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. radiation, there are higher incidents of dermatomyositis,” says Dr. Aggarwal. But again, he cautions, you probably have 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 characteristics rashes,” says Dr. Aggarwal. Patients usually get referred to a dermatologist, who can recognize these specific, distinct rashes and then do a skin biopsy to reach a conclusive diagnosis, he adds, though the 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 polymyositis, dermatomyositis, necrotizing myopathy, and juvenile myositis may also take an immunosuppressant drug, such as methotrexate, mycophenolate, or azathioprine, 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.

A third-line treatment is immunoglobulin, a blood product obtained from blood plasma rich in antibodies, and usually given through an IV. This also has side effects and is very expensive.

“Between these first-, second-, and third-line treatments, we are able to get about 70 percent of patients better,” says Dr. Aggarwal. The remaining patients will have to take a different combination of meds or enroll in clinical trials.

“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.

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