The diagnostic utility of anti-melanoma differentiation-associated gene 5 antibody testing for predicting the prognosis of Japanese patients with DM.

Interstitial lung disease (ILD), especially rapidly progressive ILD (RPILD), is a major poor prognostic factor in patients with DM. We investigated the association of anti-melanoma differentiation-associated gene 5 (MDA5) antibody (Ab) with clinical characteristics and mortality in Japanese patients with DM. Seventy-nine DM patients, comprising 58 classic DM and 21 clinically amyopathic DM (CADM) patients, were enrolled. Serum Abs were screened by immunoprecipitation assays, and an immunosorbent assay (ELISA) was used for MDA5. The relationships of clinical characteristics and mortality with each Ab were investigated. Anti-MDA5 Ab was detected in 17 patients. Anti-clinically amyopathic DM 140  kDa polypeptide Abs (anti-CADM-140 Abs) were found in 16 of the 17 anti-MDA5 Ab(+) patients. Skin ulcers, palmar papules, CADM, RPILD and mediastinal emphysema were widely distributed in anti-MDA5 Ab(+) patients. Mortality at 6 months as well as 5 years was also significantly higher in anti-MDA5 Ab(+) patients than in anti-MDA5 Ab(-) patients. In a multivariable Cox regression analysis, mortality was independently associated with anti-MDA5 Ab (relative hazard 6.33; 95% CI 1.43, 28.0). All of the deaths in anti-MDA5 Ab(+) patients were attributed to respiratory failure of RPILD; however, RPILD did not worsen in any of the anti-MDA5 Ab(+) patients who survived the first 6 months. The presence of anti-MDA5 Ab identifies the characteristic skin, musculoskeletal, pulmonary and prognostic features in patients with DM. In addition, anti-MDA5 Ab seems to predict a group of patients with CADM-complicated fatal RPILD.