Polymyositis
What Is Polymyositis?
Polymyositis is a systemic inflammatory disorder that causes progressive muscle weakness and inflammation of the connective tissues in the body. This rare autoimmune condition primarily affects the skeletal muscles—the muscles responsible for movement—leading to chronic inflammation that causes muscle fiber damage and degeneration over time. Polymyositis specifically targets the muscles of the shoulders, upper arms, upper back, neck, and hips, though it can eventually affect other muscle groups as well. Unlike some muscle diseases that affect only one side of the body, polymyositis characteristically causes symmetric muscle weakness affecting both sides of the body equally.
The precise cause of polymyositis has not yet been discovered. However, many characteristics of the condition are similar to other autoimmune inflammatory diseases. In autoimmune disorders, the immune system mistakenly identifies the body's own tissues as foreign invaders and attacks them. In polymyositis, the body's antibodies that normally fight against harmful substances like bacteria or viruses instead attack muscle tissue, causing inflammation and progressive damage. Why this autoimmune response occurs remains unclear, though genetic factors may play a role in susceptibility.
Polymyositis can occur at any age but is most common among adults aged 30 to 50 years. Women are affected approximately twice as often as men. The condition is relatively rare compared to other autoimmune disorders. While it shares some features with dermatomyositis (another inflammatory muscle disease), polymyositis does not include the characteristic skin rashes seen in dermatomyositis. The condition is classified as part of a group of diseases called idiopathic inflammatory myopathies—muscle diseases of unknown cause.
The symptoms of polymyositis develop gradually over several weeks or months, progressively becoming more severe. Unlike acute muscle injuries that cause sudden pain and weakness, polymyositis has an insidious onset that can make early diagnosis challenging. Symptoms may also fluctuate over the course of weeks or months, with periods of worsening alternating with relative stability. The hallmark symptom is progressive muscle weakness that occurs symmetrically on both sides of the body—for example, affecting both shoulders equally or both hips simultaneously. This weakness particularly affects the proximal muscles (those closest to the body's center), making tasks that require lifting the arms overhead or standing from a seated position increasingly difficult.
Additional symptoms include profound fatigue that is often out of proportion to activity level. Muscle tenderness or pain may accompany the weakness, though this is less prominent than the weakness itself. Difficulty swallowing (dysphagia) can develop when the muscles of the throat and esophagus become affected, potentially leading to choking or aspiration. Speech difficulties may occur if the muscles involved in articulation weaken. Shortness of breath can develop from weakness of the muscles that assist with breathing or from complications affecting the lungs. As the condition progresses, simple activities become increasingly challenging—patients may find it difficult to raise their head when lying down, climb stairs, reach overhead, or stand up from a chair without assistance.
Polymyositis can also affect other organ systems beyond the muscles. The heart may develop inflammation (myocarditis) or abnormal rhythms. The lungs can be affected by interstitial lung disease, causing progressive breathing difficulties. In some cases, Raynaud's phenomenon (where fingers and toes change color and feel cold in response to temperature changes or stress) may develop. Unlike dermatomyositis, polymyositis does not cause the characteristic purple-red skin rash on the eyelids, face, or over the knuckles.
Nonsurgical Treatments
Polymyositis is primarily managed with medications and supportive therapies rather than surgery. With several years of treatment, it may be possible for symptoms to be significantly reduced or even eliminated in some patients. Treatment focuses on reducing inflammation, suppressing the abnormal immune response, improving muscle strength and function, and managing complications. Our doctors offer comprehensive treatment approaches to help patients maintain quality of life.
Lifestyle Modifications
While lifestyle changes cannot cure polymyositis, certain modifications can help manage the condition. Balancing rest and activity is important—adequate rest helps manage fatigue, while appropriate activity helps maintain muscle strength and prevent deconditioning. Protecting muscles from overexertion during flare-ups prevents additional damage. Nutrition plays an important role, particularly when swallowing difficulties develop. Maintaining adequate protein intake supports muscle health. Avoiding triggers such as excessive sun exposure or stress may help some patients. Energy conservation techniques taught by occupational therapists can help patients accomplish daily tasks more efficiently.
Medications & Injections
Medication is the cornerstone of polymyositis treatment. When treated early, medical therapy is usually very effective at reducing symptoms and preventing further muscle damage. Initial treatment typically includes immunosuppressant medications, with corticosteroids like prednisone being the first-line therapy to reduce muscle inflammation. High doses are often used initially, then gradually tapered to the lowest effective dose as symptoms improve. Other immunosuppressive therapies may be added or substituted, including methotrexate, azathioprine, mycophenolate, or cyclosporine, particularly when corticosteroids alone are insufficient or to allow lower steroid doses and reduce side effects. Intravenous immunoglobulin (IVIG) involves infusions of antibodies from healthy donors and can be effective for some patients, particularly those who don't respond adequately to other treatments. Experimental biological therapies targeting specific components of the immune system are being investigated and may be options in resistant cases.
Physical & Occupational Therapy
Therapeutic interventions are crucial for maintaining function and quality of life. Physical therapy exercises help maintain and gradually rebuild muscle strength, flexibility, and functionality. A carefully designed exercise program that avoids overexertion while promoting gentle strengthening can help preserve muscle mass and function. Range of motion exercises prevent joint contractures that can develop from muscle weakness. As disease activity is controlled with medication, progressive strengthening exercises can help rebuild weakened muscles. Speech therapy can be invaluable for patients who develop difficulty swallowing or speaking as well as teaching techniques to swallow safely and reduce aspiration risk. As the disease progresses, consultation with a registered dietitian may be necessary to learn how to modify diet consistency to make foods easier and safer to chew and swallow, reducing the risk of choking or aspiration pneumonia.
Supportive & Assistive Devices
Various assistive devices can help patients maintain independence as muscle weakness progresses. Mobility aids such as canes or walkers provide stability and reduce fall risk. Reaching tools, button hooks, and adapted utensils help with daily tasks when arm strength is limited. Raised toilet seats and grab bars make bathroom use safer. Orthotics or braces may help support weakened limbs. As breathing muscles weaken in severe cases, breathing assistance devices may become necessary.
Surgical Treatments
Polymyositis itself is not treated surgically, as it is a systemic inflammatory condition requiring medical management. However, surgical interventions may occasionally be needed to address specific complications or symptoms that develop as a result of the disease.
Management of Swallowing Difficulties
In severe cases where dysphagia (difficulty swallowing) becomes life-threatening or nutritional status deteriorates despite medical management, placement of a feeding tube may be necessary. A gastrostomy tube can be placed surgically or endoscopically to allow nutrition to bypass the swallowing mechanism. This is typically considered only when swallowing dysfunction is severe and persistent despite optimal medical therapy.
Treatment of Respiratory Complications
If severe respiratory muscle weakness develops or if interstitial lung disease progresses significantly, mechanical ventilation support may become necessary. In some cases where swallowing dysfunction leads to recurrent aspiration pneumonia, surgical procedures to protect the airway might be considered, though these are rare.
Contracture Release
Prolonged muscle weakness can lead to joint contractures (permanent shortening of muscles and tendons). In some cases, surgical release of contractures may be necessary to restore range of motion and improve function, though this is typically a last resort after physical therapy and splinting have been exhausted.
The prognosis of polymyositis varies significantly among patients. With early diagnosis and aggressive treatment, many patients experience significant improvement in symptoms and can maintain good quality of life. Some patients achieve complete remission, while others have a chronic relapsing-remitting course requiring ongoing treatment. A small percentage of patients may develop severe complications or disease that is resistant to treatment. Regular monitoring by a rheumatologist or neurologist experienced in treating inflammatory myopathies is essential. Blood tests to monitor muscle enzyme levels and immune system markers help guide treatment adjustments. Patients require ongoing surveillance for medication side effects and disease complications affecting the heart and lungs.