Background Over the last few years, the discovery of myositis-specific antibodies (MSAs) has allowed the characterization, besides the three main entities: polymyositis (PM), dermatomyositis (DM) and inclusions body myositis, of new clinical entities such as the antisynthetase syndrome (ASS) and autoimmune necrotizing myopathy.
Objectives The objective of this study was to determine the clinical profile of myositis patients with MSAs.
Methods From January 2006 to February 2014, we collected the myositis patients with positive MSAs followed in Internal Medicine Department of “La Rabta” Hospital. Autoantibodies were detected by immunodot (Euroimmun®), to identify anti-Mi-2, anti-SRP and anti-synthetase antibodies (anti-Jo-1, anti-PL-7, anti-PL-12, anti -EJ and anti-OJ).
Results We identified 26 patients (22 women) with one or more MSAs. The average age was 44 years. Eleven patients had two MSAs and only one patient had three MSAs.
The anti-Mi-2 autoantibodies were positive in 11 cases: 8 cases of DM, 2 cases of PM and one case of ASS. The myopathy was benign in all cases, the oesopharyngeal and respiratory disease was observed in 5 cases and cardiac involvement in one case.
The anti-SRP antibodies were positive in 16 cases: 13 cases of DM, 2 cases of PM and one case of ASS. The myopathy was acute onset in 2 cases, the oesopharyngeal disease was observed in 11 cases and the respiratory disease in 9 cases. Cardiac involvement was observed in 2 cases.
Anti-Jo-1 antibodies were positive in 9 cases, 7 cases of ASS and 2 cases of DM, the anti-PL-7 antibodies were positive in a case of PM and the anti-PL-12 antibodies were positive in two cases of DM. Anti-EJ and anti-OJ antibodies were negative in all cases.
Conclusions Usually, anti-Mi-2, anti-synthetases and anti-SRP antibodies are associated with benign DM, ASS, autoimmune necrotizing myopathy and cardiac involvement respectively. These associations were not confirmed in our study which reflects an atypical profile of MSAs in Tunisian patients.
Disclosure of Interest None declared