Anti-OJ autoantibodies: Rare or underdetected?

Anti-OJ autoantibodies are rare myositis-specific autoantibodies that have been described to target isoleucyl-tRNA synthetase. Routinely used multiplex assays perform poorly in detection of anti-OJ antibodies. In this manuscript, we review the existing literature on critical issues in detection of anti-OJ and the clinical features associated with anti-OJ. The challenging detection with line/blot immunoassays and ELISAs is most likely related to the characteristics of the autoantigen involved, which is part of a multi-enzyme synthetase complex. Anti-OJ autoantibodies might therefore be more aptly termed anti-OJ complex autoantibodies. Anti-OJ autoantibodies are associated with the anti-synthetase syndrome, with interstitial lung disease (ILD) frequently being the sole manifestation. Myositis, present in the majority of patients with anti-OJ antibodies, is more severe than in patients with other anti-aminoacyl-tRNA synthetases. Most patients respond to glucocorticoid therapy. As detection of anti-OJ is relevant for treatment, reliable and practical detection is needed. Meanwhile, clinicians need to be aware of the possibility of anti-OJ in patients with ILD, isolated or in combination with myositis.