Objectives: The aim of this study was to evaluate the effect of prior corticosteroid (CS) use on the presence of inflammatory infiltrates (InI) in muscle biopsies from dermatomyositis (DM).
Methods: Sixty-five muscle biopsy samples were obtained at the time of DM diagnosis. The patients were divided into the following three groups according to the degree of the InI present in the muscle biopsies: (I) minimal InI present only in an interstitial area (endomysium, perimysium) or in a perivascular area; (II) moderate InI in one or two areas of the interstitium or of the perivascular area; and (III) moderate InI throughout the interstitium or intense inflammation in at least one area of the interstitium or of the perivascular area.
Results: All groups (I=17, II=16 and III=32) were comparable regarding the patient age at the time of the muscle biopsy, gender, ethnicity distribution, time interval between the muscle biopsy and the symptom onset, clinical manifestations, degree of muscle weakness, autoantibodies and serum muscle enzyme measurements (p<0.05). The median (interquartile) duration of CS use [7 (0-60), 6 (0-105) and 14 (0-30) days in groups I, II and III, respectively] and the median cumulative CS dose used [560 (0-2100), 1005 (0-2850) and 875 (0-2850) mg] were similar between the groups (p>0.05).
Conclusions: Previous CS use did not influence the presence or the degree of inflammatory infiltrates found in muscle biopsies in DM with clinical and laboratory disease activity. Therefore, muscle biopsies should be performed in this population, including patients currently undergoing CS therapy.