A Changing Anti-Neutrophil Cytoplasmic Antibody Profile in a Patient With a Diagnosis of Eosinophilic Granulomatosis With Polyangiitis

This report describes a hitherto unique case of eosinophilic granulomatosis with polyangiitis (EGPA), a subtype of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis. The patient was an 81-year-old man whose clinical course involved notable changes in the ANCA profile, specifically a transition from positive proteinase 3 (PR3)-ANCA to myeloperoxidase (MPO)-ANCA, followed by simultaneous positivity for both. The patient's medical history included bronchial asthma, allergic rhinitis, sinusitis, and multiple comorbidities. Despite being initially PR3-ANCA-positive, subsequent admissions demonstrated MPO-ANCA positivity along with eosinophilic manifestations, highlighting the complexity of diagnosis of EGPA. Diagnostic evaluation included imaging, serological markers, and clinical symptoms, which collectively supported the classification of EGPA. Notably, this case challenges the conventional diagnostic paradigms and emphasizes the evolving nature of ANCA profiles in vasculitis. The shift in ANCA profile prompted a reevaluation of the patient's diagnosis and treatment strategy. This case underscores the importance of considering fluctuations in ANCA in patients with a diagnosis of EGPA, management decisions, and potential implications for disease progression. Further research is warranted to elucidate the mechanisms underlying changes in ANCA and their clinical significance in vasculitis.