Polymyositis (pol-e-mi-o-SI-tis) is a persistent inflammatory muscle disease that causes weakness of the skeletal muscles, which control movement. Medically, polymyositis is classified as a chronic inflammatory myopathy — one of only three such diseases.
Polymyositis can occur at any age, but it mostly affects adults in their 30s, 40s or 50s. It's more common in blacks than in whites, and women are affected more often than men are. Polymyositis signs and symptoms usually develop gradually, over weeks or months.
Remissions — periods during which symptoms spontaneously disappear — are rare in polymyositis. However, treatment can improve your muscle strength and function.
Signs and symptoms of polymyositis appear gradually, so it may be difficult to pinpoint when they first started. They may also fluctuate from week to week or month to month.
Polymyositis signs and symptoms include:
Polymyositis typically affects the muscles closest to the trunk, particularly those in your hips, thighs, shoulders, upper arms and neck. The weakness is symmetrical, meaning it involves muscles on both the left and right sides of your body.
The disease worsens over time. As muscle weakness progresses, you might find it difficult to climb stairs, rise from a seated position, lift objects or reach overhead.
When to see a doctor
The exact cause of polymyositis is unknown, but the disease shares many characteristics with autoimmune disorders, in which your immune system attacks normal body components. Normally, your immune system works to protect your healthy cells from attacks by foreign substances, such as bacteria and viruses. If you have polymyositis, an unknown cause may act as a trigger for your immune system to begin producing autoimmune antibodies (autoantibodies) that attack your body's own tissues. Many people with polymyositis show a detectable level of autoantibodies in their blood.
Possible complications of polymyositis include:
Concerns during pregnancy
Preparing for your appointment
You'll probably first bring your symptoms to the attention of your family doctor, who may refer you to a rheumatologist — a doctor who specializes in the treatment of arthritis and other diseases of the joints, muscles and bone.
What you can do
Prepare a list of questions ahead of time to help make the most of your limited time with your doctor. For polymyositis, some basic questions to ask your doctor include:
In addition to the questions that you've prepared to ask your doctor, don't hesitate to ask questions during your appointment.
What to expect from your doctor
Tests and diagnosis
Diagnosis of polymyositis isn't always easy and can be a lengthy process. Even though the attempt to diagnose your condition may be frustrating, remember that an accurate diagnosis is necessary to receive appropriate treatment.
In addition to a thorough physical exam, your doctor will likely use other tests to confirm a diagnosis of polymyositis:
Treatments and drugs
Although there's no cure for polymyositis, treatment can improve your muscle strength and function. The earlier treatment is started in the course of polymyositis, the more effective it is, leading to fewer complications. However, as with many conditions, no single approach is best; your doctor will tailor your treatment strategy based on your symptoms and how well they respond to therapy.
Corticosteroids are medications that suppress your immune system, limiting the production of antibodies and reducing muscle inflammation, as well as improving muscle strength and function.
Your doctor may prescribe a very high dose to begin with, and then decrease it as your signs and symptoms improve. Improvement generally takes about two to four weeks, but you may take the medication for several months. Prolonged use of corticosteroids can have serious and wide-ranging side effects, which is why your doctor may gradually taper the dose of medication down to low levels.
Because of the potential for serious side effects, your doctor may recommend supplements to combat them, such as calcium and vitamin D, and may prescribe medications to help protect your bones.
Additional immunosuppressive therapies
However, there aren't many scientific studies to date about the effectiveness of these agents on polymyositis. If your doctor prescribes one of these medications, you'll be closely monitored for side effects. These medications can be expensive and, because they're experimental for treating polymyositis, may not be covered by insurance.
Other treatment approaches
Coping and support
Living with a chronic autoimmune disease can make you wonder at times whether you're up to the challenge. To help you cope, try supplementing your medical care with the following suggestions:
Last Updated: 2011-07-07
© 1998-2014 Mayo Foundation for Medical Education and Research (MFMER). All rights reserved. A single copy of these materials may be reprinted for noncommercial personal use only. "Mayo," "Mayo Clinic," "MayoClinic.com," "Mayo Clinic Health Information," "Reliable information for a healthier life" and the triple-shield Mayo logo are trademarks of Mayo Foundation for Medical Education and Research.
Terms and conditions of use