Polymyositis is an idiopathic inflammatory myopathy characterized by CD8+ T-cell-mediated destruction of skeletal muscle fibers, causing symmetric proximal muscle weakness. The autoimmune attack involves cytotoxic T lymphocytes that recognize and directly invade non-necrotic muscle fibers expressing MHC class I molecules (normally absent on healthy muscle), with endomysial inflammatory infiltration surrounding and destroying individual myocytes. Clinical presentation includes insidious onset of symmetric proximal muscle weakness (difficulty climbing stairs, rising from a chair, lifting arms above the head), dysphagia from pharyngeal muscle involvement (aspiration risk), and elevated serum creatine kinase (CK, often 10-50 times normal) from muscle fiber destruction. Interstitial lung disease occurs in a subset of patients, particularly those with anti-Jo-1 (anti-histidyl tRNA synthetase) antibodies, as part of the antisynthetase syndrome (myositis, ILD, mechanic's hands, Raynaud phenomenon, arthritis, fever). The nurse monitors muscle strength using manual muscle testing, monitors CK and aldolase levels as markers of disease activity, assesses swallowing function and implements aspiration precautions, monitors respiratory function (FVC), administers immunosuppressive therapy (high-dose corticosteroids, methotrexate, azathioprine, or IVIG) as prescribed, and coordinates physical therapy to maintain function while avoiding exercise-induced muscle...