Beyond Chronic Rhinosinusitis: Multisystem Granulomatosis With Polyangiitis Presenting With Cavitary Pulmonary Nodules and Sinonasal Destruction.

Granulomatosis with polyangiitis (GPA) is a rare necrotizing vasculitis of small- to medium-sized vessels characterized by granulomatous inflammation, most commonly involving the upper respiratory tract, lungs, and kidneys. Early manifestations are frequently non-specific and may resemble chronic allergic or infectious rhinosinusitis, delaying recognition until destructive sinonasal, pulmonary, renal, neurologic, or cutaneous involvement emerges. Cutaneous vasculitis and cavitary pulmonary nodules further complicate the diagnostic process by raising concern for infection or malignancy. We report a 69-year-old woman with years of refractory nasal congestion and recurrent epistaxis who developed progressive sinonasal obstruction, septal perforation, palpable purpura, peripheral sensory symptoms, renal urinary abnormalities, and bilateral cavitary pulmonary nodules. Laboratory evaluation demonstrated PR3-ANCA/c-ANCA positivity, elevated inflammatory markers, anemia of inflammation, mild renal dysfunction, and urinalysis with proteinuria and microscopic hematuria. Computed tomography demonstrated destructive sinonasal disease and bilateral cavitary pulmonary nodules. Nasal biopsy showed necrotizing granulomatous inflammation with small to medium vessel vasculitis, confirming GPA. High-dose systemic glucocorticoids and rituximab-based induction therapy were initiated with Pneumocystis jirovecii pneumonia prophylaxis and multidisciplinary rheumatology, otolaryngology, pulmonology, and nephrology follow-up. This case is not presented as a unique manifestation of GPA but as an educational reminder that chronic rhinosinusitis becomes a diagnostic trap when accompanied by epistaxis, septal destruction, pulmonary cavitation, purpura, neuropathic symptoms, or urinary abnormalities. Earlier recognition of this pattern may prevent irreversible organ damage.