Background: Polymyositis (PM) is systemic disease affecting mainly the skeletal muscles. The typical form of PM affects muscles of the shoulder and/or pelvic girdle, and dominating symptom is muscle
pain, and there are distinctive changes in electromyography. The diagnosis is confirmed by
muscle biopsy.
Case report: We presented two cases of PM that are characterized by atypical localisation of symptoms in
the first one, and the intensity of organ complications in the second one. The first patient had
the pain and contraction only in both gastrocnemius muscles in spite of laboratory changes taking in evidence systemic inflammation and defects in electromyography of other skeletal muscles. There was the quick improvement of general state with therapeutic application of glucocorticoids that was additional confirmation of inflammatory background of the disease in this patient. The second presented patient was more typical if concerning localisation but the extent of the muscle damage expressed by activity of creatine phosphokinase (reaching
100.000 units/litre) was unusual. The systemic complications such as heart failure, renal failure, and gastric mucosal damage are proves of severity of the disease.
Conclusions: Atypical course of PM that is very difficult to diagnose in initial phase of the disease can be found in clinical practice. The disease especially in elderly patients may characterize by
a severe course with a number of the organ involvement.

Keywords: polymyositis