Isolated nasal septal involvement in granulomatosis with polyangiitis: Radiologic features and literature review.

Granulomatosis with polyangiitis is a necrotizing granulomatous vasculitis that predominantly involves the upper and lower respiratory tracts and the kidneys. Although sinonasal manifestations are common, they are often nonspecific and can mimic benign inflammatory conditions, leading to delayed diagnosis. In contrast, strictly localized disease limited to the nasal septum without systemic involvement is exceptionally rare. We report the case of a 27-year-old woman presenting with persistent nasal obstruction and rhinorrhea. Nasal endoscopy revealed a septal perforation. Computed tomography demonstrated focal nasal septal lysis without paranasal sinus involvement. Laboratory investigations showed markedly elevated c-ANCA levels, and histopathological examination of a septal biopsy confirmed granulomatosis with polyangiitis. Systemic imaging revealed no pulmonary or renal involvement, supporting a localized form of the disease. The patient was treated with systemic corticosteroids and methotrexate, resulting in clinical remission at 5 months. This case highlights the crucial role of imaging in detecting early structural abnormalities and guiding biopsy in atypical presentations of GPA. Early recognition of localized disease is essential to initiate appropriate immunosuppressive therapy and prevent progression to systemic involvement.