B43-10 Unmasking PL-12 Antisynthetase Syndrome: A Diagnostic Challenge

Abstract Introduction Anti-PL-12 antisynthetase syndrome (Anti PL-12-ASyS) is defined by autoantibodies against alanyl-tRNA synthetase (PL-12). While ASyS presents with varying manifestations of inflammatory myopathy, Anti PL-12-ASyS often reveals as interstitial lung disease (ILD) preceding myositis symptoms. Prompt recognition is crucial to direct appropriate immunosuppressive therapy. Case A 52 -year old African American female with hypertension, tobacco use, and obesity presented with shortness of breath and hypoxemic respiratory failure. 7 months prior, she had similar symptoms requiring noninvasive ventilation. CT Chest revealed multi-lobar bilateral airspace consolidations and ground glass opacities (GGOs). Her echocardiogram noted diastolic dysfunction. Labs included absolute eosinophil count of 300, elevated procalcitonin, leukocytosis, elevated ESR, CRP. Basic rheumatologic and infectious workup was negative. Initial diagnosis was viral pneumonia, volume overload secondary to heart failure with preserved ejection fraction, and obesity hypoventilation syndrome. She had persistent oxygen requirements and lack of response to antibiotics and diuretics. She initially declined bronchoscopy. HRCT 1 month later showed worsening consolidations. Steroids were started for treatment of presumed organizing pneumonia (OP) with improvement in symptoms. CT 3 months later showed improved GGOs. With prednisone tapered off, her respiratory failure reemerged. Her symptoms improved again with steroids. She underwent a bronchoscopy with bronchoalveolar lavage and transbronchial biopsies. Pathology was notable for chronic inflammation and lung parenchyma with OP. Finally, a myositis panel was sent which was positive for anti-PL-12 autoantibodies. At that point, she was started on rituximab, weaned off steroids, and was enrolled in pulmonary rehabilitation. Her outpatient pulmonary function tests (PFTs) initially showed severe restriction with reduced gas exchange. 6 months later, with rituximab therapy, our patient was off of home oxygen with resolution of symptoms and improvement in PFTs. Her follow up CT showed resolution of GGOs, now revealing underlying architectural distortion and NSIP. Conclusion PL-12 associated ILD presents with more severe lung involvement and worse outcomes in black patients. It can also radiographically present with an NSIP and OP overlap. Prompt and aggressive immunosuppressive therapy is paramount to avoid clinical deterioration. Our patient had multiple comorbidities that could have explained her initial respiratory failure. She lacked overt stigmata of dermatomyositis. This made arriving at her diagnosis uniquely challenging. Myositis-associated ILD should be suspected when a patient presents with rapidly worsening respiratory failure without any clear cause, radiographic signs of NSIP/OP, even in the absence of myopathy. Our case demonstrates the diagnostic challenges in identifying CTD-ILD and the importance of prompt treatment. This abstract is funded by: none