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.