Clinical Phenotype of Japanese Patients with Dermatomyositis—Classification Based on Dermatomyositis-Specific Autoantibodies

Abstract

Objectives: To correlate the precise specificity of autoantibodies in Japanese dermatomyositis (DM) patients with their clinical phenotypes. Methods: Serum samples from 94 adult DM patients (67 with classical DM and 27 with clinically amyopathic dermatomyositis, CADM) were screened for autoantibodies using immunoprecipitation assays. Patients with antibodies against aminoacyl transfer RNA synthetase (ARS), Mi-2 or who had other autoantibodies were assessed for clinical symptoms and laboratory findings. Results: Sera from 27 of 94 DM patients (29%) were found to have anti-ARS antibodies. Nineteen (20%) had anti-CADM-140/MDA5, 5 (5%) had anti-Mi-2, and 8 (6%) had anti-p155/TIF1-γ. Anti-MJ/NXP-2 was not found in our series of adult DM. Seventeen patients with anti-ARS had fever and 22 had arthritis and interstitial lung disease (ILD), compatible with a diagnosis of anti-ARS syndrome. Seventeen of 19 (89%) with anti-CADM-140/MDA5 had ILD, 16 (84%) of whom developed rapidly progressive ILD (RP-ILD). Four of 5 (80%) with anti-Mi-2 had heliotrope rash and/or Gottron’s sign/papules, and 2 (40%) had V-sign and/or shawl-sign rash, whereas no ILD or malignancy was detected. As seen with anti-Mi-2-positive patients, a low frequency of ILD (13%) was found in patients with anti-p155/TIF1-γ but 6 of 8 (75%) had malignancy during their course. The frequency of ILD was significantly higher in patients with anti-ARS or anti-CADM-140/MDA5 compared with anti-Mi-2 or anti-p155/TIF1-γ (81% and 89%, respectively). It should be noted that anti-CADM-140/MDA5-positive patients suffered significantly more RP-ILD compared to patients with anti-ARS (84% vs. 7%, P < 0.0001). On the other hand, anti-p155/TIF1-γ positive patients had a significantly higher rate of malignancy compared with anti-ARS-, anti-CADM-140/MDA5-and anti-Mi-2-positive patients (75% vs. 7%: P = 0.0004, 5%: P = 0.0006, 0%: P = 0.02, respectively). Conclusions: These results indicate that in addition to antibodies previously identified as specific for DM, autoantibodies newly found in these patients are useful for stratifying them into clinical subgroups.