The spectrum of idiopathic inflammatory myopathies: a Tunisian cohort

Background Idiopathic inflammatory myopathies (IIM) encompass a heterogenous group of auto-immune diseases. The identification of myositis specific antibodies (MSA) and their associations with distinct phenotypes has improved the categorization of these conditions. Objective The aim of this study was to describe and report the clinical and immunological characteristics of IIM among Tunisian patients. Method A retrospective study conducted in the internal medicine department at the Rabta University Hospital Center over 22 years, including adult patients with IIM according to the American college of rheumatology/European league against rheumatism (ACR/EULAR) classification criteria and Connors’ criteria for anti-synthetase syndrome (ASS). Inclusion body myositis and myositis associated with other conditions were excluded. Demographic, clinical, and immunological characteristics were analyzed and compared. Results Ninety-seven patients were included (Male/female ratio= 0.36, mean age = 48.4 +- 13.8 years). Muscular involvement was present in 88% of patients, affecting locomotor muscles (88%), gastrointestinal (43%), laryngeal (10%), cardiac (8%), and respiratory (1%) systems. Muscle weakness was primarily noted in the pelvic girdle (81%), scapular region (74%), axial muscles (20%), and distal muscles (5%). Myolysis was observed in 77% of patients, and histological evidence of myositis in 73%. Diffuse interstitial pneumonia (DIP) was present in 45% of patients, cutaneous involvement in 85%, and articular involvement in 48%. MSAs were detected in 52% of patients. Analysis revealed significantly higher frequencies of amyopathic forms, DIP, palmar hyperkeratosis, and articular involvement in the ASS group. The DM group exhibited higher frequencies of gastrointestinal signs, Gottron’s papules, heliotrope rash, photosensitive rashes, ulcerations, and skin necrosis. The NAM group had higher frequencies of gastrointestinal signs, myolysis, and lower frequencies of DIP and cutaneous involvement. Conclusion Our findings corroborate previously established clinico-immunological associations reported in the literature underscoring the need for a combined clinico-serological approach in classifying IIM.