Clinical Significance of Anti‐Histidyl‐tRNA Synthetase (Jo1) Autoantibodies

The clinical significance of a discovery of anti-histidyl-tRNA synthetase (Jo1) autoantibodies patients was established in the early diagnosis of antisynthetase syndrome (ASS) as the common form of this pathology is characterized by interstitial lung disease (ILD), inflammatory muscle disease, and production of anti-Jo1 autoantibodies. However, the specificity of such autoantibodies has to be evaluated in daily clinical practice. In this study, the clinical and prognostic profiles of 45 patients displaying anti-Jo1 autoantibodies were determined. Among 36 patients with a titer of anti-Jo1 autoantibodies above the cutoff value suggested by the manufacturer (40 AU/mL), three different groups were identified. The first group (n = 26) suffered from a complete or incomplete ASS and showed anti-Jo1 autoantibodies mostly above 60 AU/mL. A second group (n = 7) suffered from another autoimmune disease, that is, a systemic lupus erythematosus, cutaneous lupus and rheumatoid arthritis, and Crohn's disease with anti-Jo1 autoantibodies mostly below 60 AU/mL. The third group (n = 3) did not suffer from any autoimmune disease and presented anti-Jo1 autoantibodies below 60 AU/mL. The nine doubtful cases (titer of anti-Jo1 autoantibodies of 30-39 AU/mL) were from patients with no ASS nor myositis. Only 27 out of 45 patients showed antinuclear antibodies with 15 sera showing a pattern characteristic of anti-Jo1 autoantibodies by indirect immunofluorescence on HEp2 cells. In conclusion, this study underlines the need to search for anti-Jo1 autoantibodies even if antinuclear antibodies are negative by indirect immunofluorescence and underlines the usefulness of anti-Jo1 antibodies of titer above 60 AU/mL in the diagnosis of complete or incomplete ASS.