Asymptomatic and slowly progressive anti-MDA5 ILD: A report of three cases deviating from a notoriously rapidly progressive ILD.

Background: Anti-melanoma differentiation-associated gene 5-positive (anti-MDA5) dermatomyositis (DM) is a rare autoimmune disease associated with rapidly-progressive interstitial lung disease (RP-ILD.) The reported morbidity and 6-month mortality remains high from 33 to 66 % with RP-ILD most often developing within three months of diagnosis. Most cases require aggressive immunosuppression with combination therapy. Asymptomatic or slowly progressive cases of anti-MDA5 ILD are not well described in the literature. We report three cases of Latino patients with asymptomatic or slowly progressive anti-MDA5 ILD. Case 1: A 54-year-old woman from Honduras with known diagnosis of anti-MDA5 dermatomyositis presented for ILD. She denied respiratory symptoms. Computed tomography (CT) chest showed multifocal patchy areas of scattered groundglass opacities throughout all lobes of the lungs, predominately in a subpleural distribution within the lower lobes. Pulmonary function testing (PFTs) showed mild-to-moderate restriction. She was treated with mycophenolate mofetil monotherapy for her skin manifestations. At 18 months follow-up, she denied respiratory symptoms, and PFTs were normal. Case 2: An 80-year-old man from Cuba was seen in pulmonary clinic to establish care. He was diagnosed with pulmonary fibrosis 11 years earlier with positive anti-MDA5. He denied respiratory symptoms. PFTs showed moderate obstruction and mild to moderate restriction. CT chest showed reduced lung volumes and findings compatible with usual interstitial pneumonia. He was started on nintedanib. Fifteen months following the initial visit, his PFTs remained stable. Follow-up CT chest showed stable pulmonary fibrosis. At all subsequent visits, he reported mild to moderate, slowly progressive dyspnea on exertion and was maintained on nintedanib. Thirteen years after his initial ILD diagnosis, he was diagnosed with pancreatic adenocarcinoma. Case 3: A 70-year-old woman from Peru presented to pulmonary clinic with cough for two months. She also reported pain in several metacarpophalangeal joints. She denied dyspnea. Rheumatologic serologies revealed positive anti-MDA5. PFTs were normal. Her cough was treated with cough suppressants and resolved. At a subsequent visit 8 months after presentation, she denied respiratory symptoms, and her joint pain remained mild. Given her lack of respiratory symptoms and normal PFTs, she was not initiated on ILD-specific treatment. Conclusions: While anti-MDA5 ILD is certainly associated with RP-ILD, clinicians should maintain awareness that there may be cases of asymptomatic or slowly progressive ILD as well.