Autoantibody profiles in the sera of European patients with myositis

Objective-To determine the prevalence of myositis specific autoantibodies ( MSAs) and several myositis associated autoantibodies (MAAs) in a large grou p of patients with myositis. Methods-A total of 417 patients with myositis from 11 European countries (1 98 patients with polymyositis (PM), 181 with dermatomyositis (DM),and 38 wi th inclusion body myositis (IBM)) were serologically analysed by immunoblot , enzyme linked immunosorbent assay (ELISA) and/or immunoprecipitation. Results-Autoantibodies were found in 232 sera (56%), including 157 samples (38%) which contained MSAs. The most commonly detected MSA was anti-Jo-1 (1 8%). Other anti-synthetase, anti-Mi-2, and anti-SRP autoantibodies were fou nd in 3%, 14%, and 5% of the sera, respectively. A relatively high number o f anti-Mi-2 positive PM sera were found (9% of PM sera). The most commonly detected MAA was anti-Ro52 (25%). Anti-PM/Sc1-100, anti-PM/Sc1-75, anti-Mas , anti-Ro60, anti-La, and anti-U1 snRNP autoantibodies were present in 6%, 3%, 2%, 4%, 5%, and 6% of the sera, respectively. Remarkable associations w ere noticed between anti-Ro52 and anti-Jo-1 autoantibodies and, in a few se ra, also between anti-Jo-1 and anti-SRP or anti-Mi-2 autoantibodies. Conclusions-The incidence of most of the tested autoantibody activities in this large group of European patients is in agreement with similar studies of Japanese and American patients. The relatively high number of PM sera wi th anti-Mi-2 reactivity may be explained by the use of multiple recombinant fragments spanning the complete antigen. Furthermore, our data show that s ome sera may contain more than one type of MSA and confirm the strong assoc iation of anti-Ro52 with anti-Jo-1 reactivity.