Abstract Introduction Antisynthetase syndrome (ASyS) is a rare autoimmune myositis characterized by the presence of antisynthetase antibodies, inflammatory myopathy, arthritis, and interstitial lung disease (ILD). Pulmonary involvement may precede or overshadow other systemic manifestations, often leading to repeated misdiagnoses of pneumonia and delayed recognition of the underlying autoimmune etiology. Description A 39-year-old woman with diabetes and no prior pulmonary disease experienced four hospitalizations over seven months for recurrent pneumonia. She developed progressive dyspnea and hypoxemia, with oxygen saturation falling as low as 70% on room air, requiring 2 liters of oxygen by nasal cannula at home. Despite multiple antibiotic courses, her respiratory symptoms persisted.Outpatient chest computed tomography (CT) revealed persistent bilateral patchy opacities and mediastinal lymphadenopathy. Bronchoscopy was unrevealing, and a corticosteroid trial provided minimal benefit. Over time, she developed profound fatigue, prolonged morning stiffness, symmetric small-joint arthralgias, and proximal muscle weakness limiting daily activities.Upon readmission for worsening hypoxemia (requiring 4 liters of oxygen), she was found to be positive for rhinovirus and Methicillin-resistant Staphylococcus aureus in the setting of persistent CT findings, likely contributing to her acute respiratory decompensation. Leukocytosis ranging from 11,000 to 19,000 cells/µL was noted. Rheumatology evaluation revealed markedly elevated creatine kinase (CK) (10,053 U/L) and aldolase (84.6 U/L), positive anti-Jo-1 antibody, elevated ESR and CRP, and positive Ribonucleoprotein antibody. Magnetic Resonance Imaging (MRI) of the thighs demonstrated diffuse intramuscular edema consistent with inflammatory myopathy. She met Solomon’s and Connor’s criteria for Antisynthetase Syndrome. Treatment with intravenous methylprednisolone for three days, followed by oral prednisone (1 mg/kg/day) and mycophenolate mofetil 500 mg twice daily, led to a decline in CK to approximately 2,300 U/L and gradual improvement in strength, though she remained oxygen-dependent at her prior baseline. She was discharged on immunosuppression with referral to a combined Pulmonary-Rheumatology ILD clinic. Discussion This case illustrates a rapidly progressive form of Antisynthetase Syndrome in which ILD preceded overt myositis, leading to multiple hospitalizations for presumed infection before diagnosis. The clinical course of ASyS-related ILD can be rapidly progressive (RP-ILD), evolving over days to weeks and often refractory to standard immunomodulatory regimens. Less than one-third of patients develop this phenotype, which is often associated with delayed diagnosis, irreversible lung injury, and poor prognosis. Early recognition of autoimmune features in patients with recurrent or antibiotic-refractory pneumonias, unexplained ILD, or hypoxemia should raise suspicion for RP-ILD and prompt multidisciplinary evaluation and timely initiation of immunosuppressive therapy to improve outcomes. This abstract is funded by: None
Avendano et al. (Fri,) studied this question.