An Evolving Clinical Phenotype Preceding the Diagnosis of Eosinophilic Granulomatosis With Polyangiitis: A Case Report.

Eosinophilic granulomatosis with polyangiitis (EGPA), formerly known as Churg-Strauss syndrome, is a rare antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis characterised by eosinophilic inflammation, granulomatous disease and necrotising small- to medium-vessel vasculitis. Diagnosis is often delayed because clinical manifestations evolve gradually and mimic more common respiratory, infectious or inflammatory conditions. We describe a 53-year-old woman with recurrent hospital admissions over a two-year period and persistent low-positive ANCA serology, during which there was initially insufficient clinical evidence of systemic vasculitis. She subsequently presented with respiratory symptoms, palpable purpura, oral ulceration and nasal crusting. Investigations demonstrated peripheral eosinophilia (9.1 × 10⁹/L) and bilateral pulmonary inflammatory infiltrates. The emergence of eosinophilia alongside pulmonary, cutaneous and upper airway involvement provided sufficient clinical evidence to support a diagnosis of EGPA. High-dose corticosteroid therapy resulted in rapid clinical improvement and normalisation of the eosinophil count. This case highlights how EGPA may evolve over time before sufficient clinical features emerge to support the diagnosis. Recurrent non-specific presentations associated with eosinophilia and evolving multisystem involvement should prompt continued clinical reassessment, even when previous investigations have been inconclusive.