Background Idiopathic inflammatory myopathies (IIM) are autoimmune diseases characterized by inflammation of skeletal muscle tissue. There are several clinical entities: polymyositis (PM), dermatomyositis (DM), the inclusions body myositis (MI), the anti-synthetase syndrome (ASS), etc.
Objectives The objective of this study was to determine the prevalence of a wide range of autoantibodies in patients with IIM.
Methods We identified all patients with IIM addressed by the Internal Medicine Department, between January 2006 and February 2014 for immunological tests.
The myositic-specific antibodies MSA (anti-Mi-2, anti-Jo-1, anti-PL-7, anti-PL-12, anti-EJ, anti-OJ, anti-SRP) and the myositic-associated antibodies MAA (anti-Ku, ani-PM-Scl75, anti-PM-Scl100, anti-Ro-52) were detected by immunodot (Euroimmun®).
Other antibodies were also investigated: anti-nuclear antibodies (ANA) by indirect immunofluorescence on Hep2 cells (Biorad®), anti-soluble nuclear antigens antibodies (anti-ENA), anti-DNA antibodies, anti-thyroperoxydases (ATPO), anti-thyroglobulins (Athy) and rheumatoid factors (RF) by Elisa (Human®).
Results We identified 54 patients including 10 with PM, 36 with DM and 8 with ASS. It was 41 women and 13 men with an average age of 44 years [range: 12-74 years]. More than half (28/54) had an associated autoimmune disease.
MSA were detected in 38 patients (70%). Among these antibodies, anti-Mi-2, Jo-1, PL-7, PL-12 and SRP were positive in 20%, 17%, 2%, 4% and 30% of cases, respectively. No patient had anti-EJ or anti-OJ.
Among the MAA, anti-Ku, anti-PM-Scl75, anti-PM-Scl100 and anti-Ro-52 were positive in 20%, 13%, 20% and 44% of cases, respectively.
ANA were positive in 87% of cases, of which only 28% were at a strong title ≥1/800. Anti-ENA, anti-DNA, ATPO, Athy and RF were positive in 33%, 7%, 41%, 15%, and 37% of cases, respectively.
Three patients (6%) had no antibodies.
Conclusions We report a high prevalence of MSA in Tunisian patients with IIM, especially anti-SRP. Furthermore, the presence of several MAA might be related to associated autoimmune diseases but can also reflect a particular autoimmune profile in these patients.
Disclosure of Interest None declared