| Inflammatory | | Polymyositis | | Dermatomyositis | | Inclusion body myositis | | Juvenile dermatomyositis | | Vasculitis | | Overlap syndromes – Systemic lupus erythematosus, systemic sclerosis, rheumatoid arthritis, Sjögren's syndrome | | Rheumatoid arthritis, Sjögren's syndrome | | Endocrine disorders | | Hypothyroidism | | Cushing's syndrome (or exogenous steroid administration) | | Electrolyte disorders | | Hypokalemia | | Hypophosphatemia | | Hypocalcemia | | Hypernatremia or hyponatremia | | Metabolic myopathies | | Disorders of carbohydrate, lipid, and purine metabolism | | | Drugs and toxins | | Illicit drugs – Cocaine, heroin | | Alcohol | | Glucocorticoids | | Other - Colchicine, antimalarial drugs, HMG-CoA reductase inhibitors, penicillamine, zidovudine | | Infections | | Viral – Influenza, parainfluenza, Coxsackie, HIV, cytomegalovirus, echovirus, adenovirus, Epstein-Barr virus | | Bacterial – Pyomyositis, Lyme myositis | | Fungal | | Parasitic – Trichinosis, toxoplasmosis | | Rhabdomyolysis | | Crush trauma | | Seizures | | Alcohol abuse, including hyperkinetic state with delirium tremens | | Exertion, especially with environmental heat illness | | Vascular surgery | | Malignant hyperthermia | | Inherited myopathies | | Acid maltase deficiency | | Muscular dystrophy | |
