Cluster Analysis Using Anti–Aminoacyl-tRNA Synthetases and SS-A/Ro52 antibodies in Patients With Polymyositis/Dermatomyositis

OBJECTIVE: Although several autoantibodies have been identified for polymyositis/dermatomyositis (PM/DM) diagnosis, the clinical impact of these antibodies is yet to be elucidated. METHODS: Patients with PM/DM at Okayama University Hospital from 2012 to 2016 were historically enrolled, and antibody profiles were analyzed using line immunoassay. Hierarchical cluster analysis was performed based on serological analysis of anti-aminoacyl-tRNA synthetase (ARS) antibodies, including anti-Jo-1, PL-7, PL-12, EJ, OJ, and SS-A/Ro-52 antibodies. Clinical symptoms and relapse proportions were compared among these clusters. RESULTS: Sixty-one patients were enrolled in this study: 28 were diagnosed with PM, and 33 were diagnosed with DM. The following 3 clusters were determined: 1 (n = 10), anti-Jo-1 and anti-SS-A/Ro-52 antibodies double positive (10/10, 100%); 2 (n = 24), anti-SS-A/Ro-52 antibody positive (20/24, 83%), anti-Jo-1 antibody negative (24/24, 100%), and anti-ARS antibodies (excluding anti-Jo-1 antibody) positive (15/24, 63%); and 3 (n = 27), anti-Jo-1 and anti-SS-A/Ro52 antibodies double negative (26/27, 96%). The proportion of patients who relapsed was significantly lower in cluster 3 than it was in clusters 1 and 2 (risk ratio, 0.37; 95% confidence interval, 0.17-0.83; p = 0.026 and risk ratio, 0.42; 95% confidence interval, 0.20-0.89; P = 0.019, respectively). There was no difference in the proportion of relapsed patients between clusters 1 and 2. CONCLUSIONS: Our cluster analysis shows that anti-SS-A/Ro52 or any anti-ARS antibodies or both might be relevant to clinical outcomes.