Abstract
Granulomatosis with polyangiitis (GPA, Wegener’s granulomatosis) is one of the antineutrophil cytoplasmic antibody (ANCA)-associated small vessel vasculitis involving various organs such as nasal septum, sinuses, upper respiratory tract, lungs, and kidneys. GPA is pathologically characterized by necrotizing granulomatous inflammation ANCA-associated small vessel vasculitis represent a major challenge in hospital admissions; therefore, early and accurate diagnosis with aggressive treatment is essential to improve the disease outcome.
Renal involvement of Granulomatosis with Polyangiitis is characterized morphologically by extensive crescent formation (extracapillary proliferation in Bowman's space), and clinically by crescentic or rapidly progressive glomerulonephritis that causes hematuria, erythrocyte casts, and proteinuria with progressive loss of renal function.
The diagnosis of Granulomatosis with Polyangiitis is established most securely by biopsy specimens showing the triad of vasculitis, granulomata, and large areas of necrosis (known as geographic necrosis) admitted with acute and chronic inflammatory cells. Usually, renal involvement is severe and is the leading cause of mortality. The combination of high-dose corticosteroids and cyclophosphamide is the mainstay of treatment for vasculitis and disease resistance to this combination is rare.

Key words: Granulomatosis with Polyangiitis, vasculitis, crescentic glomerulonephritis, ANCA-small vessel vasculitis, Anti-GBM glomerulonephritis