How does involvement of the kidney manifest clinically and pathologically in Granulomatosis with polyangiitis?
Clinical evidence of renal disease occurs in approximately 15% to 30% of patients with GPA on presentation, ultimately affecting 50% to 80% patients. The pathologic renal lesion is a pauci-immune, focal and segmental, necrotizing GN . In more severe cases, crescentic GN may occur. Immunofluorescence studies reveal little or no deposition of immunoglobulin (Ig), immune complexes, or complement, thus the designation pauci-immune. Renal vasculitis of larger vessels and granulomas are uncommon.
Most patients with GN have asymptomatic renal disease, manifesting as active urinary sediment (hematuria, pyuria, proteinuria, and cellular casts) with variable degrees of disturbance of renal function. Patients with more severe renal involvement may develop progressive renal disease leading to acute or chronic renal failure.