Polymyositis

Polymyositis is a rare disease that causes your immune system to attack your muscles, leading to chronic inflammation and weakness that affects both sides of the body. While there is no cure, understanding the condition and available treatments can help you manage symptoms and maintain your quality of life.

Table of contents

• What is polymyositis?
• What causes polymyositis?
• Who gets polymyositis?
• Symptoms and complications
• How is polymyositis diagnosed?
• Treatment options
• Living with polymyositis
• What to expect in the future

What is polymyositis?

Polymyositis is a rare disease that causes muscles to become irritated and inflamed. The muscles eventually start to break down and become weak^[1]. It belongs to a group of diseases called inflammatory myopathies, which are conditions where the immune system causes long-lasting inflammation in the muscles^[1].

The term itself describes the condition: “poly” means many, “myo” means muscle, and “itis” means inflammation^[5]. If you have polymyositis, you may have inflammation in multiple muscles at the same time. It usually affects the muscles on or near the center of your body, including in your arms, hips and thighs, chest, back, abdomen, and neck^[1].

• Shoulders
• Hips
• Thighs
• Upper arms
• Neck
• Back
• Abdomen
• Chest

Polymyositis is different from other similar conditions. Unlike dermatomyositis, which also causes a skin rash, polymyositis only affects the muscles without skin involvement^[6]. It also differs from inclusion body myositis, which develops more slowly over months to years and typically affects older individuals^[4].

What causes polymyositis?

The exact cause of polymyositis is not known, but it is thought to be an autoimmune disease. This means that the body’s immune system, which normally protects you against harmful invaders like viruses and bacteria, makes a mistake and attacks your own tissues instead^[1].

In polymyositis, abnormal activation of certain immune cells called cytotoxic T lymphocytes (CD8 cells) and macrophages attack muscle tissues. These cells damage the inner layers of skeletal muscles, called the endomysium, causing inflammation and eventually leading to muscle weakness^[4].

While the disease can start on its own with no clear cause, sometimes other health conditions or reactions to medications can trigger it^[1]. Several factors may be involved in developing polymyositis, including both genetic and environmental influences^[5].

Some viral infections have been linked to polymyositis, including COVID-19, influenza (the flu), the common cold, and HIV. Certain viruses like hepatitis C and human T-lymphotropic virus 1 (HTLV-1) may cause this inflammatory muscle damage by affecting muscle tissues directly^[1][4].

You’re more likely to develop polymyositis if you already have other autoimmune diseases, including lupus, rheumatoid arthritis, scleroderma, or Sjogren’s syndrome^[1][2].

Who gets polymyositis?

Polymyositis is rare. Experts estimate that it affects fewer than 25 out of every 100,000 people every year^[1]. It can affect people of any age and gender, though it is rarely seen in persons under age 18^[5][14].

The disease most commonly affects adults in their 30s, 40s, or 50s, with the highest rates being seen in the 35-44 and 55-64 year old age groups^[2][15]. It affects women more often than men — about twice as many females are affected compared to males^[1][5].

Anyone can develop polymyositis, but certain groups of people are more likely to experience it, including females, people living with other autoimmune diseases, and people between 30 to 60 years old^[1].

Symptoms and complications

The symptoms of polymyositis are caused by inflammation and swelling in your muscles. The muscle weakness happens on both sides of your body and usually affects muscle groups closer to the center of your body, such as hips, shoulders, thighs, upper arms, upper back, and neck^[6].

The most common symptoms include^[1][2]:

• Muscle weakness (especially in your shoulders and hips)
• Muscle pain and tenderness
• Trouble swallowing (dysphagia)
• Difficulty talking
• Trouble breathing or shortness of breath (dyspnea)
• Fatigue (feeling tired all the time)
• Joint pain
• Fever
• Stiffness (especially right after you wake up in the morning)
• Weight loss

Signs and symptoms usually develop gradually, over weeks or months^[2][3]. Most people notice within weeks if they have developed muscular weakness, although some may have the disease for months or even years before it is realized^[5].

The progressive muscle weakness can make even simple movements hard to do^[3]. You might have trouble with activities you usually can do, including^[1]:

• Standing up after sitting
• Climbing stairs
• Lifting objects
• Reaching over your head
• Raising your arms over your head
• Rising from a chair
• Carrying things

Other muscles sometimes affected are those in the neck, making it difficult to raise the head when lying down^[5]. If the muscles in your throat are affected, you may have problems swallowing, which in turn may cause weight loss and poor nutrition. The voice may become nasal or deeper in quality^[5].

Depression and a general feeling of unhappiness is very noticeable and can be an indication of the disease before any sign of muscle weakness^[5].

Possible complications of polymyositis include^[2]:

• Difficulty swallowing, which may cause you to breathe food or liquid into your lungs (aspiration)
• Aspiration pneumonia, which can develop if you breathe in food or liquids
• Weight loss and malnutrition from swallowing difficulties

Some people may also have lung problems, which can cause difficulty breathing^[15]. In rare cases, individuals with severe and progressive muscle weakness may develop respiratory failure or pneumonia^[14].

Some polymyositis symptoms can cause life-threatening complications. You should go to the emergency room or call 911 (or your local emergency services number) if you feel like you can’t breathe or swallow^[1].

How is polymyositis diagnosed?

There are no simple tests to diagnose polymyositis. It often takes time before doctors know for sure you have it^[6]. A healthcare provider will diagnose polymyositis with a physical exam and some tests^[1].

Your doctor will take your medical history to rule out other conditions and may also test your muscle strength^[6]. They’ll ask about your symptoms and examine the muscles that are feeling weak or experiencing symptoms. Your provider will ask you how it feels when you do certain movements or motions^[1].

If your doctor suspects you have polymyositis, he or she might suggest some of the following tests^[9]:

Blood tests: A blood test will let your doctor know if you have elevated levels of muscle enzymes, which can indicate muscle damage. Blood tests can also detect specific autoantibodies associated with different symptoms of polymyositis, which can help in determining the best medication and treatment^[1][9].

Electromyography (EMG): This test involves inserting a thin needle electrode through the skin into the muscle. Electrical activity is measured as you relax or tighten the muscle, and changes in the pattern of electrical activity can confirm a muscle disease. The doctor can determine the distribution of the disease by testing different muscles^[9].

Magnetic Resonance Imaging (MRI): A scanner creates cross-sectional images of your muscles from data generated by a powerful magnetic field and radio waves. Unlike a muscle biopsy, an MRI can assess inflammation over a large area of muscle^[1][9].

Muscle biopsy: During this test, a small piece of muscle tissue is surgically removed for laboratory analysis. Analysis may reveal abnormalities, such as inflammation, damage, certain proteins or enzyme deficiencies. After the doctor sees you and reviews the results of your testing, a muscle biopsy may be required to confirm the diagnosis of polymyositis^[9][15].

Your provider will use a few tests to diagnose polymyositis. Some of these tests will rule out other conditions that can cause similar symptoms^[1].

Treatment options

Although there’s no cure for polymyositis, treatment can improve your muscle strength and function^[9]. The earlier treatment is started in the course of polymyositis, the more effective it is — leading to fewer complications^[9].

Treatment of polymyositis is based on experience because of the rarity of the disease and the lack of large controlled studies. However, several approaches have proven helpful^[11].

Corticosteroids: Drugs such as prednisone are often the first-line treatment. The standard treatment for polymyositis is a corticosteroid drug, given either in pill form or through a vein^[9][11]. These medications help to reduce inflammation and swelling, and suppress damaging immune responses^[13]. Typically, the dose is 1 mg per kilogram of body weight per day, either as a single dose or in divided doses. This high dose is usually continued for 4-8 weeks, until muscle enzyme levels return to normal ranges^[11].

Long-term use of high-dose corticosteroid therapy, however, may produce unwanted side effects, such as decreased bone density, increased tissue swelling, or weight gain^[13]. Your healthcare provider will closely monitor you for disease activity and adverse effects^[11].

Immunosuppressive drugs: For some affected people, therapy with other drugs that suppress the immune system may be beneficial^[13]. Immunosuppressive agents are indicated in patients who do not improve with steroids within a reasonable period (about 4 weeks) or in whom adverse effects from corticosteroids develop^[11]. These medications include azathioprine, methotrexate, mycophenolate mofetil, tacrolimus, or cyclosporine^[9][13].

Biologic agents: Additional treatment options used in combination may include the monoclonal antibody rituximab. Rituximab may be an approach to treatment for patients with difficult-to-treat polymyositis^[11][13].

Intravenous immunoglobulin (IVIG): IVIG has been used for the short-term treatment of cases that don’t respond to steroids. IVIG therapy can be effective for some patients and can improve muscle strength and reduce inflammation^[11][13].

Treatment plans are typically tailored to meet the needs of the affected person and ongoing monitoring is required to improve the treatment approach^[13]. Your doctor will tailor your treatment strategy based on your symptoms and how well they respond to therapy^[9].

In some cases, affected people may require prolonged treatment throughout their lives, while in others, therapy may be gradually withdrawn as symptoms resolve^[13].

Physical therapy: A tailored exercise program can help maintain and improve muscle strength and flexibility. Physical therapists work with patients to create a safe and effective program^[1][13]. Physical therapy is usually recommended to prevent muscle shortening and to regain muscle strength and range of motion^[14].

Occupational therapy: Occupational therapists help patients adapt their daily activities and use assistive devices to maintain independence and quality of life^[13].

Speech and swallowing therapy: For patients experiencing difficulty swallowing or speaking, specialized therapy can help improve these functions^[13].

Supportive treatment can help manage complications such as swallowing or breathing difficulties or abnormalities of the heart, lungs, or digestive system^[13].

Living with polymyositis

Living with polymyositis requires adjustments and self-care strategies to manage symptoms and maintain quality of life. There are many things you can do at home to ease muscle pain and inflammation^[16].

Self-care approaches that may help include massages, taking breaks from work or working from home when needed, and eating more healthy, anti-inflammatory foods^[16]. A balanced diet rich in anti-inflammatory foods can support overall health and well-being. A nutritionist can provide personalized dietary recommendations^[13].

To juggle lack of energy, work, and exercise, it’s essential to ask yourself every day and throughout the day how much energy you have and what’s possible to do without pushing yourself too hard. Make sure you save your precious energy by not participating in activities that you know are just too much. If you are careful about how you use your energy, committing only to what is most important and meaningful, you will have more stamina^[21].

The best way to deal with expectations from family regarding mobility and energy is to be honest and up front. Tell them that even though you don’t look sick, you have an “invisible disease” that restricts your mobility and drains your energy. Tell them in advance that sometimes you may say no to an invitation that may be too stressful for you, or you may excuse yourself from an event if you get too tired to carry on, and they shouldn’t take that personally. Reassure them that you are doing your very best to cope with polymyositis and be clear with them about what does and doesn’t help^[21].

To manage mobility challenges, make sure you are always one step ahead so that you always have what you need for support. For example, get a cane, walker, or wheelchair before you need it, so that you don’t end up without the appropriate equipment when you get to that stage. And always be safe and make sure you’re not pushing yourself beyond your capacity^[21].

Managing stress is important when dealing with the challenges of polymyositis. Here are helpful stress reducers^[21]:

1. Create a morning routine that lets you ease into your day — no rushing
2. Spend time only with positive people who support you
3. Say no to what doesn’t feel right for you
4. Do something you enjoy every day — even for just a moment
5. List three things at the end of every day that went well, and ease into sleep with a relaxing evening routine (no technology an hour before bed)

What to expect in the future

The outlook for polymyositis varies. Most people respond fairly well to therapy, but some have a more severe disease that does not respond adequately to therapies and are left with significant disability^[14].

Response to treatment varies, based on the complications. As many as 1 in 5 people may die within 5 years of developing the condition^[7]. However, many people, especially children, recover from the illness and do not need ongoing treatment. For most adults, however, drugs that suppress the immune system are needed to control the disease^[7].

Some people recover completely, while others experience greatly diminished symptoms for long periods of time. Several years of treatment to suppress the immune system may be necessary to achieve these results^[13].

The outlook for people with lung disease associated with certain antibodies is poor despite current treatment^[7]. The major causes of death are cancer and lung disease^[7].

Polymyositis can become inactive, meaning it will go away and come back. During the inactive periods, you may feel well and have few or no symptoms^[6].

Visit a healthcare provider if you notice new muscle weakness, pain or fatigue. Seek medical attention if you develop unexplained muscle weakness^[1][2].