RAPIDLY PROGRESSIVE INTERSTITIAL LUNG DISEASE IN ASSOCIATION WITH MDA5 ANTIBODY DERMATOMYOSITIS

Abstract

SESSION TITLE: Medical Student/Resident Diffuse Lung Disease SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: October 18-21, 2020 INTRODUCTION: Clinically Amyopathic Dermatomyositis (CADM) is a subtype of dermatomyositis (DM) characterized by the presence of cutaneous lesions, without clinical evidence of muscle weakness. The presence of autoantibodies against Melanoma Differentiation-Associated protein 5 (MDA5) in this group is highly associated with rapidly progressive interstitial lung disease (RP-ILD) and a worse prognosis. We present a case of anti-MDA5 associated RP-ILD to illustrate the importance of screening for MDA5 in patients with CADM and DM. CASE PRESENTATION: Our patient was a 45-year-old woman with a history of hypothyroidism, seronegative inflammatory polyarthritis treated with hydroxychloroquine, and notably, a history of biopsy-proven DM with a negative myositis-specific antibodies (MSA) panel (which did not include MDA5 antibodies). She had been successfully treated for DM, and maintained in remission with oral steroids. Four years following the diagnosis of DM, she presented with insidious and gradually progressive dyspnea for over a year. Physical examination was unremarkable. Pulmonary function testing showed moderate restrictive lung disease. Chest X-ray was notable for bibasilar interstitial changes. Computed tomography (CT) scan of the chest revealed nonspecific, bilateral ground-glass opacities in the middle and lower lung zones, with associated bibasilar bronchiectasis in the affected areas (Figure 1). Bronchoscopic evaluation, including transbronchial biopsy, was performed, which was negative for malignancy or infection. Open lung biopsy was obtained via robotic-assisted thoracoscopy from the affected lobes, with histopathology revealing interstitial fibrosis with multiple fibrotic foci without clear evidence of honeycombing. The pattern was suggestive of usual interstitial pneumonia (UIP). Repeat testing for MSA revealed an elevated anti-MDA5 antibody level at 22 SI. The patient was consequently diagnosed with RP-ILD in conjunction with CADM, prompting the initiation of oral prednisone and azathioprine. DISCUSSION: Anti-MDA5 antibodies recognize the RNA helicase encoded by MDA5, a protein that is involved in innate immune processes. The presence of anti-MDA5 antibodies in patients with CADM has been linked to the presence of RP-ILD, and portends a poor prognosis. The mechanism of this autoantibody production is not fully understood. One meta-analysis found that the presence of these antibodies was 77% sensitive and 86% specific for the identification of RP-ILD. Additionally, anti-MDA5 antibodies can be utilized to predict clinical outcomes and monitor disease activity in these patients. Due to its high mortality rate from respiratory failure, immediate therapy with high-intensity combination immunosuppression is essential once the diagnosis is made. CONCLUSIONS: This case highlights the importance of screening for anti-MD5 antibodies in patients with CADM to elucidate their risk of developing RP-ILD. Reference #1: Li L, Wang Q, Yang F, et al. Anti-MDA5 antibody as a potential diagnostic and prognostic biomarker in patients with dermatomyositis. Oncotarget. 2017;8(16):26552–26564. doi:10.18632/oncotarget.15716 Reference #2: Chen, Z., Cao, M., Plana, M.N., Liang, J., Cai, H., Kuwana, M. and Sun, L. (2013), Utility of Anti–Melanoma Differentiation–Associated Gene 5 Antibody Measurement in Identifying Patients With Dermatomyositis and a High Risk for Developing Rapidly Progressive Interstitial Lung Disease: A Review of the Literature and a Meta-Analysis. Arthritis Care & Research, 65: 1316-1324. doi:10.1002/acr.21985 DISCLOSURES: No relevant relationships by Komal Ejaz, source=Web Response No relevant relationships by Dan Kazmierski, source=Web Response No relevant relationships by Bassel Noumi, source=Web Response No relevant relationships by Pius Ochieng, source=Web Response No relevant relationships by NISHANT SHARMA, source=Web Response No relevant relationships by Yichen Wang, source=Web Response