Granulomatosis with polyangiitis (GPA)
GPA is a primary vasculitis characterized by:
- • Upper and lower respiratory tract involvement with granulomatous vasculitis of mostly small vessels, extravascular granulomatous inflammation, and necrosis (varying levels of each of these three features may be encountered at a particular site).
- • Glomerulonephritis (GN) that is pauci-immune, focal and segmental, necrotizing, and often crescentic.
- • Strong association with c-ANCA and anti-PR3 antibodies .
Generalized GPA implies involvement of all three major anatomic sites (upper respiratory tract, lungs, and kidneys). Limited GPA is defined as the absence of renal involvement (a more strict definition also excludes patients with pulmonary hemorrhage, orbital pseudotumor, progressive neuropathy, and central nervous system [CNS] disease). Limited GPA tends to present as a granulomatous disorder without vasculitic features. Only 10% of cases evolve to generalized GPA.
Although GPA is considered a primary vasculitis syndrome, the inflammatory changes, including granulomas, often occur in parenchymal sites outside vessel walls ( extravascular granulomatous infiltration). Interestingly, granulomas are rarely seen in the kidneys.
