B43-23 Fulminant Anti-MDA5 Amyopathic Dermatomyositis Presenting Rapidly Progressive Interstitial Lung Disease and ARDS in an Underserved Urban Population

Abstract Introduction Anti-melanoma differentiation-associated gene 5 (MDA5)- positive amyopathic dermatomyositis is a rare, fatal disease causing rapidly progressive interstitial lung disease (RP-ILD), usually without overt muscle weakness. Diagnosis is difficult, especially in underserved areas, due to limited resources and overlapping conditions. Case A 60-year-old male from Honduras with hypertension, hyperlipidemia, pre-diabetes, coronary artery disease, and a history of smoking presented after a syncopal episode and progressive exertional dyspnea. The patient was tachypneic and hypoxemic, requiring oxygen. Initial evaluation showed elevated lactate and transaminitis. No skin rash or muscle weakness was reported. Chest imaging revealed bilateral submassive pulmonary emboli and peripheral curvilinear densities suggestive of scarring and ground-glass opacities. Broad-spectrum antibiotics and anticoagulation were started for presumed pneumonia and pulmonary embolism, respectively. The patient remained persistently hypoxemic with severe acute respiratory distress syndrome (ARDS), subsequently intubated after trial of non-invasive ventilation. Serial imaging showed worsening of bilateral ground-glass opacities with areas of honeycombing in the lingula, right middle, and bilateral lower lobes, suspicious for ILD. Infectious, autoimmune, and hypersensitivity workup were initially unrevealing, and bronchoscopy with BAL was non-diagnostic. Given refractory hypoxemia and ARDS, venovenous ECMO was initiated along with high-dose corticosteroids. Serologies returned positive for anti-MDA5 and anti-SSA antibodies, confirming amyopathic dermatomyositis-associated RP-ILD. The patient received rituximab and cyclophosphamide. Subsequently, CMV PCR became positive, and ganciclovir therapy was started for CMV pneumonitis. Despite maximal therapy including ECMO and continuous renal replacement therapy, the patient’s condition deteriorated, and the patient ultimately died. Discussion Amyopathic dermatomyositis-associated RP-ILD (MDA5+ DM-RP-ILD) is a rare but lethal cause of acute respiratory failure. Patients often present with minimal or no muscle weakness, nonspecific respiratory symptoms, and rapidly progressive bilateral ground-glass opacities, progressing to ARDS despite supportive care. Poor prognostic indicators include older age, smoking history, severe hypoxemia, extensive radiographic involvement, and ECMO therapy. These were present in our patient and contributed to the fulminant course. An underserved urban setting may further compound outcomes with limited access to rheumatologic consultation or myositis-specific antibody testing. Early recognition and prompt initiation of combination immunosuppression —typically high-dose glucocorticoids with a calcineurin inhibitor plus cyclophosphamide or rituximab —improve outcomes. Multiorgan failure remains common, causing poor survival. CMV pneumonitis in this patient highlights vulnerability to opportunistic infections under intense immunosuppression, which can exacerbate ILD. This case underscores the need for awareness of anti-MDA5 RP-ILD in resource-limited hospitals serving underserved communities. Early serologic testing and timely immunosuppression may represent an opportunity for recovery. This abstract is funded by: None