How to diagnose polymyositis

Polymyositis can be diagnosed with the following four conditions: 1. Acute or subacute symmetrical proximal and pelvic muscle weakness with tenderness, difficulty in squatting, standing up, lifting, swallowing, etc., weakened or disappeared tendon reflexes. 2. Elevated muscle enzymes, mainly by creatine kinase, phosphate dehydrogenase or transaminase in the liver. 3. EMG shows myogenic damage. 4. Abnormal muscle biopsy, showing partial or complete necrosis of muscle fibers, and giant cell phagocytosis, inflammatory cell infiltration in interstitial area or around blood vessels, mainly lymphocytes, different thickness of muscle fiber section, interstitial fiber hyperplasia, muscle fiber atrophy for several weeks, inflammatory cell infiltration and fibrosis around small blood vessels.