1- Juvenile dermatomyositis (JDM) : affects children and tends to be more severe
2- Adult dermatomyositis (ADM) : typically affects adults around the age of 50
It`s pathology described as cell mediated injury targeted at striated muscle with resultant atrophy, oedema, coagulation necrosis, fibrosis and calcification.
-There is elevation of: * muscle enzymes (CK)
* elevated muscle specific antibodies
o anti RNA
o anti Mi2
Dermatomyositis may be associated with
interstitial lung disease : typically gives a patchy and subpleural consolidation with parenchymal bands.
internal malignancy : can occur as part of a paraneoplastic syndrome (e.g lung cancer)
o sheet like although at least four patterns have described with childhood dermatomyositis 4.
o classically seen affecting the thigh regions
* chest radiograph may show diaphragmatic elevation
* acroosteolysis