Hyaline arteriolar nephrosclerosis. Immunofluorescence findings in the vascular lesions.

Of 536 renal specimens examined by direct immunofluorescence in the past 2 years, 153 contained vascular deposits of C3 without associated immunoglobulin or fibrin deposition. Excluding vasculitides, renal transplants, and outside cases with inadequate clinical data, 110 were selected for further study. Light microscopy showed periodic acid-Schiff-positive hyaline vascular deposits in 83 cases, and large electron-dense deposits were identified by electron microscopy in 47 cases. Fifty-one patients had immunologic glomerular disease in addition to hyaline arteriolar nephrosclerosis. Albumin, transferrin, and alpha-2 macroglobulin were not detected in the vessel walls of several selected cases so tested, indicating that passive diffusion probably does not explain C3 deposition. However, properdin was present in 11 of 14, and C4 in two of 11. The mechanism for this association between C3 and properdin deposition and hyaline arteriolar nephrosclerosis is not clear at present, but our findings suggest possible involvement of the alternative pathway of the complement system.