ANCA-negative eosinophilic granulomatosis with polyangiitis diagnosed via external auditory canal biopsy: A case report

Eosinophilic granulomatosis with polyangiitis (EGPA) is an uncommon systemic vasculitis characterized by asthma, eosinophilia, and multisystem involvement. The diagnosis of ANCA-negative EGPA may be challenging because serological findings are often non-specific, making histopathological confirmation important. We report a case of ANCA-negative EGPA diagnosed by biopsy of the external auditory canal, an uncommon but readily accessible site of disease involvement.

A 22-year-old Mongolian woman presented with progressive chest tightness and dyspnea. Her medical history was notable for asthma and nasal polyps. She also reported bilateral ear fullness and tinnitus. Laboratory investigations demonstrated marked eosinophilia (35.8% of leukocytes), while ANCA testing was negative. Otoscopic examination revealed inflammatory changes in the left external auditory canal, and biopsy was subsequently performed. Histopathological examination showed vasculitis with prominent eosinophilic infiltration, supporting the diagnosis of EGPA. Treatment with systemic corticosteroids resulted in rapid clinical improvement. At three-month follow-up, eosinophil counts had normalized and no evidence of disease progression was observed.

This case highlights the potential diagnostic value of external auditory canal biopsy in patients with suspected ANCA-negative EGPA. Otologic manifestations may provide accessible sites for tissue sampling when histological confirmation is required. Careful otologic examination should therefore be considered during the evaluation of patients with suspected EGPA.