Polymyositis is an autoimmune inflammatory myopathy in which immune cells attack skeletal muscle, causing slowly progressive weakness of the muscles close to the trunk. It can also involve the lungs, heart and swallowing muscles, so early diagnosis matters.
Key symptoms
- Trouble climbing stairs, rising from a chair or combing hair
- Weakness that worsens over weeks to months
- Muscle aches in some patients
- Trouble swallowing or shortness of breath
What you find on exam
- Symmetric proximal muscle weakness with normal sensation
- Reflexes usually preserved
- Neck flexor weakness and a swallowing assessment
- Skin check for a rash that would point to dermatomyositis; lung crackles
Tests
- Creatine kinase and aldolase raised
- Myositis antibodies such as anti-Jo-1
- EMG and MRI of the muscles to show inflammation
- Muscle biopsy; screening for lung disease and, in adults, cancer
Treatment basics
- High-dose glucocorticoids such as prednisone
- Steroid-sparing drugs: methotrexate, azathioprine or mycophenolate
- IV immunoglobulin for severe or resistant disease
- Physical therapy and a swallowing evaluation
Red flags
- Trouble breathing or a weak cough
- Choking or aspiration with meals
- Palpitations or chest pain suggesting heart involvement
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Sources: NCCPA PANCE Content Blueprint; NBOME COMLEX-USA clinical presentations; AAMC Core Entrustable Professional Activities (Core EPAs). Written by Making Synapses. Making Synapses is not affiliated with these organizations.