[Dermatomyositis and polymyositis: the attempt to differentiate and literature review]

Dermatomyositis (DM) and polymyositis (PM) are diseases displaying the symptoms of the idiopathic muscle inflammation (IZM). The skin lesions are visible most often 3 months to 3 years prior to appearance of the muscle inflammatory process. A frequent coexistence of DM with internal organ neoplasms obliges doctors to diagnose their patients quickly. The knowledge of skin lesions allows to begin this diagnosis earlier and to initiate proper therapy. Based on the latest medical literature, the authors present: the actual classification of the idiopathic muscle inflammation, the attempt to differentiate between DM and PM regarding prognostic factors and therapy possibilities based on conducted world trials.