Abstract Introduction Antisynthetase Syndrome (ASS) is a rare autoimmune disorder characterized by interstitial lung disease (ILD), myositis, arthritis, Raynaud’s phenomenon, and mechanic’s hands. It is associated with antibodies against aminoacyl-tRNA synthetases, most commonly anti-Jo-1, though PL-12 and other variants occur. Cardiac involvement is uncommon but potentially life-threatening. Case Presentation A 25-year-old woman presented with five days of fever, malaise, vomiting, and diffuse abdominal pain. She reported a recurrent pruritic rash over her elbows and knees, progressive proximal muscle weakness, dyspnea, and chest pain. On admission, she was febrile and tachycardic. Laboratory studies revealed leukocytosis, mild hyponatremia, elevated transaminases, and marked eosinophilia. Chest CT showed multifocal ground-glass opacities with mediastinal and hilar lymphadenopathy. Despite broad-spectrum antibiotics for presumed pneumonia, she remained tachycardic with rising troponins. CTA chest and Doppler studies ruled out thromboembolism. Given persistent eosinophilia and cardiac involvement, she received intravenous methylprednisolone with partial improvement. Worsening hypoxia prompted transfer to a tertiary center. Cardiac MRI demonstrated mid-wall enhancement and diffuse fibrosis, consistent with inflammatory myocarditis. Skin biopsy revealed interface dermatitis with perivascular inflammation, consistent with dermatomyositis. Myositis panel was positive for PL-12 and SSA (Ro60) antibodies, ANA 1:160 speckled, RF, and SSB, confirming Antisynthetase Syndrome with pulmonary and cardiac involvement. She was treated with pulse-dose IV steroids, IVIG, and mycophenolate mofetil, with Pneumocystis prophylaxis. Her rash, muscle weakness, and oxygenation improved, and she was discharged on room air with a steroid taper and follow-up cardiac MRI. Discussion Cardiac involvement in ASS occurs in 10% of cases and may manifest as myocarditis, arrhythmia, or pericardial effusion. Eosinophilic myocarditis represents immune-mediated myocardial inflammation, often mimicking infection. The presence of eosinophilia with elevated troponins should raise suspicion for myocarditis in the appropriate clinical context. PL-12 positivity correlates with severe ILD and milder myositis. Cardiac MRI remains the diagnostic gold standard. Early recognition and initiation of high-dose corticosteroids are essential, with IVIG and steroid-sparing agents for long-term control. Multidisciplinary management optimizes outcomes. Conclusion ASS should be considered in patients with unexplained rash, myopathy, eosinophilia, and myocarditis. Although rare, cardiac involvement carries high morbidity, highlighting the importance of early diagnosis and prompt immunosuppressive therapy. This abstract is funded by: None
Pugalenthi et al. (Fri,) studied this question.