Significance of Small Renal Artery Lesions in Patients with Antineutrophil Cytoplasmic Antibody-associated Glomerulonephritis

Objective. Antineutrophil cytoplasmic antibody (ANCA)-associated glomerulonephritis is a vasculitis affecting the glomerular capillaries and small renal arteries. Although crescent formation has been reported to be characteristic of this condition, the significance of coexisting vasculitis affecting the small renal arteries has not been investigated. Methods. Fifty patients with ANCA-positive rapidly progressive glomerulonephritis whose renal biopsy specimens contained arterioles and/or interlobular arteries were retrospectively evaluated. Cellular crescents and/or necrotizing glomerulonephritis were noted in all 50 patients. Ten patients had vasculitis of the small renal arteries (group A) and 40 patients were without such vasculitis (group B). The clinical features of these 2 groups were compared. Results. Group A comprised 4 patients who had granulomatosis with polyangiitis (GPA) and 6 with microscopic polyangiitis (MPA), while group B included 1 patient with GPA and 39 with MPA. No patient in either group had eosinophilic granulomatosis with polyangiitis. The C-reactive protein (CRP) level was significantly higher in group A compared with group B (11.58 +/- 6.19 vs 2.7 +/- 3.55 mg/dl, p < 0.05), and pulmonary involvement was more frequent in group A than group B (80% vs 37.5%, p < 0.05). Conclusion. In patients with ANCA-positive glomerulonephritis, vasculitis of small renal arteries may be associated with systemic vasculitis (including pulmonary involvement) because of elevated CRP, a systemic inflammatory marker related to overproduction of interleukin 6.