A Diagnostic Dilemma: Proteinase-3 (PR3)-Positive Anti-neutrophil Cytoplasmic Autoantibodies in Eosinophilic Granulomatosis With Polyangiitis.

Eosinophilic granulomatosis with polyangiitis (EGPA) is a multifaceted diseased vasculitis typically associated with myeloperoxidase-perinuclear-anti-neutrophil cytoplasmic antibody (+MPO-P-ANCA). Although rare, the diagnosis should be considered in patients with difficult-to-control or late-onset asthma and extrathoracic disease. We present the case of a 37-year-old male with adult-onset asthma and chronic rhinitis hospitalized with pancreatitis and hypoxemia. Blood investigations demonstrated eosinophilia with elevated lipase, and bronchoscopy demonstrated multiple endobronchial lesions with elevated eosinophils on bronchoalveolar lavage. In addition, labs showed proteinase 3-specific antineutrophil cytoplasmic antibody (PR3-C-ANCA) autoantibodies, and the patient was diagnosed with EGPA. Additional differential diagnoses of parasitic infection, sarcoidosis, chronic eosinophilic pneumonia, and granulomatosis with polyangiitis (GPA) were entertained, but ultimately, the multisystemic involvement, anti-neutrophil cytoplasmic autoantibody (ANCA) positivity, bronchoscopy, and imaging findings clinched the diagnosis. This case highlights the spectrum of possible EGPA presentations and a rare case of PR3-C-ANCA with gastrointestinal manifestations.