Eosinophilic Granulomatosis With Polyangiitis Presenting as Mononeuritis Multiplex in a Diabetic Patient: Diagnostic and Therapeutic Challenges

Eosinophilic granulomatosis with polyangiitis (EGPA) is a rare antineutrophil cytoplasmic antibody (ANCA)-associated small-vessel vasculitis that may present with asthma, eosinophilia, pulmonary involvement, and peripheral neuropathy. Distinguishing EGPA-related vasculitic neuropathy from diabetic neuropathy can be particularly challenging in patients with long-standing diabetes mellitus. We present a case of a 64-year-old man with type 2 diabetes, chronic kidney disease, and asthma, who developed systemic symptoms, mononeuritis multiplex, and pulmonary haemorrhage. Laboratory tests revealed marked eosinophilia and strongly positive myeloperoxidase (MPO)-ANCA, while electrophysiological studies demonstrated asymmetric axonal neuropathy. A multidisciplinary assessment by neurology and rheumatology confirmed the diagnosis of EGPA with vasculitic neuropathy, following which treatment with corticosteroids, cyclophosphamide, plasmapheresis, and rituximab resulted in significant clinical improvement. This case highlights the importance of recognizing atypical or asymmetric neuropathies in diabetic patients and considering EGPA early to prevent irreversible organ damage.