[Epidemiological profile of dermatomyositis and polymyositis: a study conducted in the Department of Rheumatology in Marrakech].

Dermatomyositis (DM) and polymyositis (PM) are rare but serious conditions. The purpose of this study was to investigate, by a review of hospital cases, their epidemiological, clinical and evolutionary profile. We conducted a retrospective study over a 15-year period, between January 2004 and December 2019. All cases with possible or definite diagnosis according to Bohan and Peter's criteria were retained. A total of 14 patients were enrolled (8 DM and 6 PM), with an average age of 48.7 years. Sex ratio was 13F/ 1H. General signs were reported in 71% of cases. Motor deficit affected the girdle muscles in 71% of cases; 85.7% of patients had arthralgia and 14% arthritis. Erythema and periorbital edema were the predominant skin signs. Patients' assessment showed increased sedimentation rate in all cases and increased muscle enzymes in 80% of cases. Antinuclear antibodies were positive in 63% of cases. Muscle biopsy objectified inflammatory myositis in 75% of cases. Heart disease was reported in 14% of cases and lung disease in 21%. Cancer was found in 21.4% of cases. All patients received corticosteroid therapy. Improvement was reported in 88% of patients, with a relapse in 4 patients. In our context, DM is more frequent than PM, with a clear female predominance. Pulmonary disease is a heavy complication. Its association with cancers occurs commonly, hence the need for a systematic cancer screening at diagnosis and follow-up.