Clinical features of anti-TIF1-α antibody-positive dermatomyositis patients are closely associated with coexistent dermatomyositis-specific autoantibodies and anti-TIF1-γ or anti-Mi-2 autoantibodies

Objective. Myositis-specific autoantibodies (MSAs), which characterize certain forms of inflammatory myopathy, are useful in the diagnosis and prediction of prognosis in DM/PM. Anti-transcriptional intermediary factor 1-alpha (TIF1-alpha) antibodies were recently reported to be associated with cancer-associated DM in conjunction with anti-TIF1-gamma antibodies. This study aimed to identify a subset of DM patients who have anti-TIF1-alpha antibodies by using biotinylated recombinant proteins and to clarify the clinical and other serological features of DM patients with these antibodies. Methods. Sera from 202 Japanese patients with CTDs, including 108 with DM and 20 healthy controls, were screened for anti-TIF1-alpha antibodies by our novel ELISAs. Positive sera were further examined by immunoprecipitation and also investigated for the detection of anti-TIF1-gamma and anti-Mi-2 antibodies. Results. Sera from 12 patients with DM were confirmed to be positive for anti-TIF1-alpha antibodies. None of the patients with other CTDs and none of the healthy controls had the antibodies. Seven anti-TIF1-alpha-positive patients simultaneously had anti-TIF1-gamma antibodies and the other five had anti-Mi-2 antibodies, both of which are well known to be MSAs. These double-positive patients with anti-TIF1-alpha and anti-gamma antibodies included three JDM and two cancer-associated adult DM patients, whereas all the double-positive patients with anti-TIF1-alpha and anti-Mi-2 antibodies were classical adult DM. Conclusion. Although MSAs have been regarded as mutually exclusive, anti-Mi-2 antibody-positive patients simultaneously have anti-TIF1-alpha antibodies. Anti-Mi-2 antibody-positive patients are associated with classical DM without cancer even with the simultaneous presence of anti-TIF1-alpha antibodies.