Gasping for a Diagnosis - A Case of MDA-5 Positive Dermatomyositis-Related Interstitial Lung Disease

Introduction The presence of antibodies against melanoma differentiation-associated gene 5 (MDA-5) is an ominous marker that is associated with rapidly progressive interstitial lung disease (ILD) associated with clinically amyopathic dermatomyositis (CADM). Early identification along with consideration of aggressive immunomodulation with monitoring for referral for lung transplantation evaluation is critical for patient outcomes. Here, we describe the diagnostic evaluation for a patient presenting with productive cough and progressive dyspnea on exertion, eventually found to have MDA-5 positive dermatomyositis-related ILD. Description of the case A 37-year-old male with history of THC vape exposure presented with an acute febrile respiratory illness prior to the COVID pandemic. He was found on high-resolution CT imaging of his chest to have peripheral predominant bilateral ground glass opacities and underwent bronchoscopy with transbronchial biopsy of the right lower lobe, with pathology demonstrating organizing pneumonia. Infectious studies from a subsequent bronchalveolar lavage demonstrated no evidence of infection, and the patient was initiated on pulse steroids for progressive hypoxemic respiratory failure requiring ICU admission and high flow nasal cannula. Initial concern at this juncture was for e-cigarette or vaping use-associated lung injury (EVALI) because his initial infectious and autoimmune panels were negative, with concern for early progression to fibrosis. However, a subsequent extended myositis panel revealed positivity for MDA-5 antibodies. Upon completion of his pulse steroids, he was transitioned to mycophenolate mofetil with intermittent intravenous immunoglobulins targeting for cutaneous dermatomyositis manifestation in coordination with rheumatology. With titration of his immunosuppression, he was able to wean off supplemental oxygen therapy. He remains closely monitored by pulmonary function tests, 6-minute walk tests, and imaging. Discussion of the novelty and importance of the case This case demonstrates the complexity of diagnosis of rapidly progressive interstitial lung diseases, with the need for multidisciplinary management for aggressive disease phenotypes. Early, aggressive immunomodulation in coordination with rheumatology achieved disease stability for this patient and has successfully delayed need for lung transplantation evaluation.