Introduction .Polymyositis and deramatomyositis (DM)are idiopathic inflammatory myopathies. Epidemiological data on these diseases are not available in this country.Objective .Comparison of clinical and laboratory symptoms between patients with PM and DM.Methods .As part of creation of a register of patients during the period from June 2000 to October 2001 clinical data were assembled from patients and laboratory tests were made related to pathogenetic processes of these diseases.Results .A total of 67 cases of idiopathic inflammatory myopathies were assembled.Most frequent was DM in 32 cases (47.8 %),followed by PM,juvenile PM/DM,myositis with malignancy and myositis within the framework of the overlap syndrome in 17,10,6 and 2 cases (24.5 %,14.9 %, 8.9 %and 3.0 %).Comparison of patients who were assessed as DM(48 cases,72 %)with the PMgroup (19 cases,28 %)revealed that the course of PM is somewhat more serious.Significantly more frequently weakness of the distal muscles was described,Raynaud ’s phenomenon,palpitations and liminally also the trismus of mastication muscles.Global evaluation of the activity and damage on the the 5-grade Likert scale was according to patients and physicians significantly more serious in PM as compared with DM.The physicians used as compared with patients more frequently the top grade of the range.Antinuclear antibodies were positive in 50.8 %cases using indirect immunoflu- orescence on Hep-2 cells and in more than 77 %of cases when evaluated with immunoblotting, countercurrent immunoelectrophoresis and the ELISA method.The most frequently detected antibodies were anti-Jo-1 (19.4 %),anti-Mi-2 (8.1 %)and anti-Ro-52 (22.6 %).Other antibodies specific for myositis (anti-PL-7,anti-PM-Scl,anti-SRP)were represented only rarely.In 29 %positive cases on immunoblotting it was not possible to identify the specificity of the antibody and in 29 non-iden- tical patients an unknown antibody differentiating an antigen with a molecular weight of 45 kD was positive.Conclusion .Dermatomyositis is more frequent than polymyositis,some data indicate that it is less serious.When using combined methods more than 75 %of patients with idiopathic inflammatory myopathies have positive autoantibodies in serum,nevertheless only a certain pro- portion can be precisely specified.

        Key words: polymyositis,dermatomyositis,antinuclear antibodies