B43-34 Concurrent Dyspnea and Weakness: A Case of OJ Ab-Positive Interstitial Lung Disease and Myositis Following a Cancer Diagnosis

Abstract Introduction Inflammatory myopathies have a well-recognized association with interstitial lung disease (ILD) and malignancy. We present a case of steroid-responsive hypoxemic respiratory failure with radiographic ILD and concurrent OJ-Ab positive myositis after a new diagnosis of metastatic adenocarcinoma. Case Presentation A previously relatively healthy 85-year-old woman was admitted to a different hospital with 6 months of dyspnea and fatigue. In the outpatient setting, she had undergone negative cardiac workup, empiric treatment for pneumonia, and diuresis trial. On admission, she required 1-2L/min of supplemental oxygen. She had a mildly elevated leukocyte count, cardiac biomarkers, and transaminases. She was treated for pneumonia and diuresed. Computed tomography (CT) of the chest showed enlarged lymph nodes (LN), suspicious for neoplasm, and mild pulmonary scarring. Positron emission tomography revealed focal colonic activity, and she underwent para-aortic LN biopsy confirming metastatic adenocarcinoma of lower gastrointestinal origin. Her course was complicated by acute kidney injury, with peak creatinine of 5.2 from 0.7 mg/dL. She was discharged on home oxygen. 10 days later, she presented to our hospital, with an ongoing 1-3L/min oxygen requirement and stable labs. CT of the chest showed basilar predominant subpleural fibrotic changes with traction bronchiectasis (Image 1). She was noted to have myoglobinuria on urine studies prompting serum creatine kinase to be checked, which was elevated at 1616 U/L. Targeted history and examination revealed progressive proximal muscle weakness and dysphagia, though rheumatologic and exposure history were otherwise negative. On hospital day 2, she was initiated on 3 days of methylprednisolone 1g/day, after which pulmonary function tests revealed moderate restrictive impairment with moderately reduced diffusion capacity and respiratory muscle weakness. She underwent muscle biopsy confirming myositis with differential chiefly including anti-synthetase syndrome or dermatomyositis. She was discharged on a high-dose steroid taper on room air, reporting improved strength and exercise capacity. Myositis panel eventually revealed OJ-Ab positivity. Treatment for her malignancy with an immune checkpoint inhibitor was contraindicated due to myositis and ILD, and she was instead started on combination chemotherapy. Discussion OJ Ab is a myositis-specific antibody associated with anti-synthetase syndrome (AS) and is known to be frequently complicated by ILD, with up to 30% of patients developing rapidly progressive fibrosis. Though AS is not classically associated with malignancy, some studies suggest that AS may be cancer-associated in up to 11.4% of patients. Maintaining a high index of suspicion for the underlying causes of ILD remains necessary for early identification and treatment. This abstract is funded by: None