Eosinophilic Granulomatosis With Polyangiitis Presenting as a Mononeuritis Multiplex Mimicking Guillain-Barré Syndrome.

A 41-year-old Malay woman with a background of allergic rhinitis, nasal polyps, and eczema presented with bilateral foot numbness and weakness. Neurological examination revealed bilateral foot drop and sensory loss over the L5-S1 dermatomes. Nerve conduction studies showed bilateral peroneal and tibial axonal neuropathy. She was initially diagnosed with Guillain-Barré syndrome (GBS) and treated with intravenous immunoglobulin (IVIG), but showed no clinical improvement. Further evaluation revealed pansinusitis on CT imaging, vasculitic rashes, marked eosinophilia of 8.7 × 10⁹/L, and positive p-ANCA (1:160), leading to a revised diagnosis of eosinophilic granulomatosis with polyangiitis (EGPA) with mononeuritis multiplex. She responded well to corticosteroid therapy and methotrexate, with significant neurological improvement and no relapse observed at follow-up. This case highlights the diagnostic challenge of distinguishing EGPA from GBS in patients with acute neuropathy and highlights the importance of recognizing systemic features such as asthma, eosinophilia, and vasculitic signs to guide appropriate immunosuppressive treatment.