From Purpura to pulmonary hemorrhage: dermatological clues to systemic vasculitis - a case of granulomatosis with polyangiitis.

Introduction: Granulomatosis with polyangiitis (GPA) is a rare ANCA-associated vasculitis that can convincingly mimic IgA vasculitis when it presents with palpable purpura and a leukocytoclastic biopsy. Failure to perform direct immunofluorescence (DIF) and ANCA testing at presentation is a recognized cause of diagnostic delay and irreversible organ damage. Case presentation: A 47-year-old woman, previously labeled as IgA vasculitis on the basis of a leukocytoclastic skin biopsy without DIF, returned 1 year later with recurrent necrotizing leg ulcers, ENT involvement, and hemoptysis. Strong c-ANCA/PR3 positivity (>100 U/mL), microscopic hematuria, an HRCT pattern of diffuse alveolar hemorrhage, and a repeat skin biopsy demonstrating pauci-immune necrotizing leukocytoclastic vasculitis (DIF negative for IgA) confirmed GPA. Pulse methylprednisolone, followed by oral corticosteroids and IV cyclophosphamide, produced complete reversal of pulmonary hemorrhage within 2 weeks and progressive healing of cutaneous ulcers. Discussion: Persistent or recurrent cutaneous vasculitis - particularly necrotizing ulcers in an adult - should prompt ANCA testing and DIF, even when an initial diagnosis of IgA vasculitis seems plausible. Pauci-immune histology and PR3-ANCA reliably distinguish GPA from IgA vasculitis and redirect management toward induction immunosuppression. Conclusion: Early dermatologic recognition, repeat biopsy with immunofluorescence at any clinical inflection point, and timely induction therapy can reverse otherwise life-threatening alveolar hemorrhage in GPA.