All conditions
Autoimmune & connective tissue
Polymyositis
Also known as: Inflammatory myositis
An inflammatory muscle disease that causes gradual weakness in the muscles closest to the trunk.
Video lesson
Animated explainer
What it is
In polymyositis the immune system attacks muscle fibers directly. Many cases once called polymyositis are now classified more precisely using antibody tests, for example as antisynthetase syndrome or immune-mediated necrotizing myopathy.
Symptoms
Weakness in the hips, thighs, shoulders and upper arms that develops over weeks to months. Trouble climbing stairs, lifting objects or swallowing, muscle aches and sometimes shortness of breath.
How it’s diagnosed
High CK and other muscle enzymes, myositis antibodies, MRI, EMG and muscle biopsy. Lung testing looks for interstitial lung disease.
Treatment
Steroids plus a steroid-sparing medicine such as methotrexate, azathioprine or mycophenolate. IVIG or rituximab for resistant disease. Physical therapy is essential to regain strength.
Living with it
Build activity gradually with guidance from a therapist. Seek prompt care for breathing or swallowing problems.
At a glance
Category
Autoimmune & connective tissue
Also known as
Inflammatory myositis
Reviewed by Farhan Tahir, MD, FACR
Questions about your own care?
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