Background/Purpose: The anti-melanoma differentiation-associated gene 5 antibody (MDA5) was recently classified as a myositis-specific antibody (MSA), and has been associated with rapidly progressive interstitial lung disease (ILD), amyopathic dermatomyositis (aDM), mechanic’s hands, ulcerations, inflammatory arthritis, and increased mortality. This study sought to distinguish the clinical characteristics of MDA5-positive patients with and without additional MSAs.

Methods: We retrospectively identified all MDA5 positive patients who were evaluated at our center from 2015 to 2017 with suspected myositis and had myositis-associated autoantibodies tested using a commercial panel (Myomarker Panel 3, RDL Reference Laboratories). For all patients who were positive for MDA5, we collected clinical information on the presence of myopathy, skin involvement and ILD, data on the autoantibody profile, PFTs and high resolution CT pattern.

Results: In our sampling period, 62 patients were positive for 1 or more MSA, of which 13 were positive for MDA5 (20.9%). Two MDA5 positive patients had incomplete clinical data and were not included in the analysis. Of the remaining 11 patients, 7 were females and 4 were males, with mean age 56.6 years (SD 10.9). Six MDA5 positive patients also had high titers of anti-Ro/SSA-52 kDa (46.1%) (mean Ab level by ELISA 120.5, SD 52). Five of the dual-positive patients had ILD (83.3%), versus 2 of MDA5-only patients (40%) (p=0.39). Of the dual-positive patients with ILD all had nonspecific interstitial pneumonitis (NSIP), 3 of which also had organizing pneumonia (67%), while in the MDA5-only group, one had fatal acute interstitial pneumonitis (20%) and the other one had UIP (20%). All of the dual-positive patients demonstrated improvement with immunosuppressive treatment as determined by CT, PFTs and clinical evaluation (100%), while only 2 patients from the MDA5-only group did (40%) (p=0.12). Three of the 6 dual-positive patients had EMG and/or MRI evidence of myopathy (50%) compared to 2 of 5 of the MDA5-only patients (40%). Two patients in the dual-antibody group had mechanic hands while only one in the MDA-only group had it.

Conclusion: Anti-Ro/SSA-52 kDa was frequently encountered in patients with MDA5-positive myopathic disease. In these dual-positive patients, ILD and NSIP were more common compared to patients that were positive for MDA5-only. A definite trend for response to immunosuppressive treatment was seen in the dual-positive group than in the MDA5-only group. As it has been reported previously, there was a high incidence of mechanic’s hands and aDM in patients positive for MDA5. This preliminary study indicates that certain autoantibody profiles in myositis are related to pulmonary and cutaneous manifestations, and may be predictive of response to treatment. These data highlight the importance of screening for these markers. Further study is ongoing to further elucidate the association of MSA and the clinical manifestations and response to treatment response of patients with inflammatory myopathies.

« Back to 2017 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/characteristics-unique-to-mda5-and-anti-rossa-52-kda-dual-antibody-positive-patients-with-inflammatory-myopathies/