Polymyositis | |
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Micrograph of polymyositis. Muscle biopsy. H&E stain. | |
Specialty | Rheumatology |
Polymyositis (PM) is a type of chronic inflammation of the muscles (inflammatory myopathy) related to dermatomyositis and inclusion body myositis. Its name is derived from poly- 'many' myos- 'muscle' and -itis 'disease'. The inflammation of polymyositis is mainly found in the endomysial layer of skeletal muscle, whereas dermatomyositis is characterized primarily by inflammation of the perimysial layer of skeletal muscles.[1]