Myositis
Myositis is the subset of myopathy characterized by inflammation of skeletal muscle.
Pathology
Etiology
Myositides can be generally categorized by etiology as follows 1:
- inflammatory myositis
-
infectious myositis 3
- bacterial myositis (pyomyositis)
- viral myositis
- influenza myositis
- coxsackievirus B virus-related pleurodynia (Bornholm disease)
- virus-associated rhabdomyolysis
- parasitic myositis (a cause of eosinophilic myositis)
- fungal myositis (rare)
- drug-related myositis
- statin-related myositis
- trauma or iatrogenic myositis
- myositis ossificans
- radiation-induced myositis 4
Radiographic features
MRI is the gold standard modality for noninvasive evaluation of myositis, which shows classic edema signal pattern (high T2WI and STIR signal) in affected muscles. Inflamed muscles demonstrate contrast enhancement.
If chronic, T1WI will show high muscle signal indicating fat replacement and atrophy.