Clinical and Laboratory Transition Between GPA and EGPA.

Granulomatosis with polyangiitis (GPA) and eosinophilic granulomatosis with polyangiitis (EGPA) are recognized subtypes of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). Their clinical boundaries, however, may be more dynamic than assumed. We describe 2 patients illustrating sequential phenotype transitions with prominent respiratory involvement. The first patient was initially diagnosed with GPA, presenting with neuropathy, purpura, epistaxis, renal disease, and myeloperoxidase (MPO)-ANCA positivity. Six years later, she developed asthma, marked eosinophilia, and eosinophilic myocarditis, consistent with evolution toward EGPA despite stable ANCA serology. The second patient was first classified as EGPA based on eosinophilic asthma, chronic rhinosinusitis with nasal polyps, and MPO-ANCA with borderline proteinase 3 (PR3)-ANCA. After SARS-CoV-2 infection, he developed GPA-like disease with strongly positive PR3-ANCA and destructive airway involvement, including tracheobronchomalacia requiring tracheostomy and stenting. These cases highlight that recognizing this dynamic nature is essential for the timely reassessment of disease classification, prognosis, and therapeutic approach in AAV.