The spectrum of idiopathic inflammatory myopathies: a Tunisian cohort

Abstract

<ns3:p>Background Inflammatory idiopathic myopathies (IIM) are a heterogeneous group of complex connective tissue diseases (CTD), primarily characterized by inflammatory involvement of skeletal muscles. Several other organs may also be affected, including lungs, heart, skin, gastrointestinal tract, and joints. Objective Describe the clinical and immunological characteristics of IIM among Tunisian patients. Method A retrospective study conducted in the internal medicine department at the Rabta Hospital over 22 years, including adult patients with IIM according to the ACR/EULAR classification criteria, and anti-synthetase syndrome (ASS) according to Connors’ criteria. Inclusion body myositis was excluded. Demographic, clinical, and immunological characteristics were analyzed. Results Ninety-seven patients were included (Male/female ratio= 0.36, mean age = 48.4 +- 13.8 years). The ACR/EULAR criteria enabled the inclusion of 88% of the patients. Dermatomyositis (DM) was the most frequent entity (47%), followed by Polymyositis (PM) (36%) and Amyotrophic dermatomyositis (ADM) (4%). Connors criteria allowed the inclusion and classification with ASS of 33 patients, including those excluded by the ACR/EULAR criteria (12%). Muscular involvement was present in 88% of patients, affecting locomotor (88%), gastrointestinal (43%), laryngeal (10%), cardiac (8%), and respiratory (1%) muscles. Myolysis was observed in 77% of patients, and histological evidence of myositis in 73%. ILD was reported across all subgroup: ASS (85%), PM (57%), DM (17%), and ADM (100%). NSIP was the most common radiologic pattern (59%). Skin involvement (85%), consistently present in DM and ADM, affected 91% of ASS patients. Joint involvement (48%) was predominantly polyarticular (68%). Myositis-specific antibodies (MSAs) were detected in 52% of patients, with a predominance of anti-synthetase antibodies (ASAs). Another CTD was noted in 24% of patients and cancer in 17% of patients. Conclusion Our study underscored the clinical diversity among IIM patients and the systemic nature of these diseases, where muscular involvement is not always uniform.</ns3:p>