C41-30 When Pneumonia Isn’t Pneumonia: Granulomatosis With Polyangiitis Masquerading as Infection

Abstract Introduction Persistent respiratory symptoms often lead to repeated antibiotic use for presumed infection. When symptoms fail to resolve, clinicians must expand the differential diagnosis. Granulomatosis with polyangiitis (GPA), a small-vessel vasculitis, can mimic community-acquired pneumonia and requires early recognition to prevent progression and organ damage. Case Presentation A 40-year-old woman with no prior medical history presented with several months of cough, dyspnea, and intermittent hemoptysis. She had received multiple outpatient antibiotic courses for “pneumonia” and “strep throat” without improvement. She also reported worsening symptoms of sinusitis for the past year. On admission, she was hypoxemic with a diffuse petechial rash on her lower extremities. Laboratory evaluation revealed elevated ESR and CRP, normal eosinophil level, normal renal function, and negative blood and sputum cultures. Chest CT demonstrated bilateral consolidations and nodular opacities. Given her occupation as a farm worker with frequent animal contact, zoonotic infections were initially considered. However, all infectious studies, including bacterial, fungal, and viral panels, were negative. Autoimmune testing revealed positive c-ANCA and PR3 antibodies. Bronchoscopy with biopsy was attempted but aborted due to desaturation; bronchoalveolar lavage cultures were negative. A skin biopsy from the petechial rash confirmed leukocytoclastic vasculitis. The patient was started on high-dose intravenous methylprednisolone, resulting in rapid clinical improvement and near resolution of infiltrates on repeat imaging. Based on serology and biopsy findings, a diagnosis of GPA presenting as nonresolving pneumonia was established. Discussion This case illustrates the diagnostic challenge of differentiating autoimmune vasculitis from infectious pneumonia. While renal involvement is classic in GPA, its absence can delay diagnosis. Environmental exposures and partial antibiotic responses may further confound the clinical picture. Skin findings and autoimmune testing provided crucial diagnostic clues, underscoring the need for vigilance when “pneumonia” fails to resolve despite standard therapy. Prompt initiation of immunosuppressive therapy can lead to dramatic recovery and prevent irreversible damage. This abstract is funded by: NONE