Periaortitis in eosinophilic granulomatosis with polyangiitis.

This report discusses a patient in his late 60s with a diagnosis of eosinophilic granulomatosis with polyangiitis (EGPA) who was found to have radiological periaortitis. He presented with acute mononeuritis multiplex and constitutional symptoms. Investigations revealed marked eosinophilia, positive myeloperoxidase (MPO) antibodies and imaging evidence of periaortitis. Nerve conduction studies showed axonal mononeuropathies, and a sural nerve biopsy confirmed a vasculitic neuropathy with eosinophilic infiltrates. He was treated with high-dose corticosteroids and intravenous cyclophosphamide, with substantial neurological improvement, and later transitioned to maintenance azathioprine. His course was complicated by a pulmonary embolism. Radiological follow-up demonstrated remission of periaortitis. This case emphasises the diagnostic challenges of distinguishing EGPA from mimics such as IgG4-related disease and highlights the importance of recognising rare large-vessel involvement in EGPA and underlines the need for vigilance regarding thromboembolic complications.