The anti-CADM-140 antibody was a marker of DM and intractable ILD and recognized IFIH1/MDA5, which is involved in innate immunity. These findings may give a new insight into the pathogenesis of DM.

No abstract

Objective Interstitial lung disease (ILD) accompanied by anti–melanoma differentiation–associated gene 5 (anti–MDA‐5)–positive dermatomyositis (DM) is often rapidly progressive and associated with poor prognosis. Because there is no established treatment, we undertook this study to prospectively evaluate the efficacy and safety of a combined immunosuppressive regimen for anti–MDA‐5–positive DM patients with ILD. Methods Adult Japanese patients with new‐onset anti–MDA‐5–positive DM with ILD (n = 29) were enrolled at multiple study centers from 2014 to 2017. They were treated with a regimen of high‐dose glucocorticoids (GCs), tacrolimus, and intravenous cyclophosphamide (IV CYC). Plasmapheresis was used if a patient's condition worsened after the regimen started. The primary end point was 6‐month survival, which was compared between this group of patients and a historical control group (n = 15) consisting of anti–MDA‐5–positive DM patients with ILD who received step‐up treatment (high‐dose GC and stepwise addition of immunosuppressant). Secondary end points were 12‐month survival rate, adverse events, and changes in laboratory data. Results The combined immunosuppressive regimen group showed significantly higher 6‐month survival rates than the step‐up treatment group (89% versus 33%; P < 0.0001). Over a period of 52 weeks, improvements in anti–MDA‐5 titers, serum ferritin levels, vital capacity, and chest high‐resolution computed tomography scores were observed. The combined immunosuppressive regimen group received IV CYC nearly 20 days earlier with shorter intervals and tended to receive plasmapheresis more often than patients undergoing step‐up treatment. Cytomegalovirus reactivation was frequently observed over 52 weeks. Conclusion A combined immunosuppressive regimen is effective for anti–MDA‐5–positive DM patients with ILD. Plasmapheresis can be used for additional effect in intractable disease. Patients should be carefully monitored for opportunistic infections during treatment.

Interstitial lung disease (ILD) is the most frequent organ involvement (found in nearly half) of myositis patients, but it reveals various clinical courses and therapeutic responsiveness according to clinical and serological subsets. Autoantibodies, as well as imaging and histopathological studies, are useful for the classification of ILD in myositis and provide useful information for predicting prognosis and determining treatment. Antisynthetase antibodies are correlated with chronic and recurrent ILD, whereas anti-CADM-140 (MDA5/IFIH1) antibodies are a marker of acute progressive ILD in clinically amyopathic dermatomyositis. Serum KL-6, SP-D, and ferritin are useful biomarkers for monitoring the activity and severity of ILD. Regarding treatment, glucocorticoids are the first-line drug, but additional immunomodulating drugs are also used in refractory patients. Cyclophosphamide and calcineurin inhibitors (cyclosporine and tacrolimus) appear to be the key drugs in the treatment of refractory myositis-ILD. Rituximab may become another candidate if these drugs are not effective.

Myositis-specific autoantibodies are useful markers for clinical diagnosis, classification and predicting prognosis of idiopathic inflammatory myopathy. To understand the etiopathogenic mechanisms of the disease it is particularly important to elucidate the nature of target autoantigens recognized by these myositis-specific autoantibodies.