Clinicopathological study of patients with mesangial isolated C3d deposition in various glomerular diseases

The clinicopathological findings of isolated mesangial C3d deposition in the absence of other complement components or immunoglobulins are summarized. 55 out of 242 individual human renal biopsies examined by immunoperoxidase microscopy had isolated C3d deposition. This group consisted of 12 patients with chronic glomerulonephritis, 8 with minimal-change nephrotic syndrome, 32 with benign recurrent hematuria, 2 with Bartter's syndrome and 1 with Raynaud's syndrome. None of these patients had a disorder of the renal function and in all the patients the disease took a benign clinical course. Light-microscopic findings indicated injuries ranging from minor glomerular abnormality to mild diffuse mesangial proliferative glomerulonephritis, and there were no other remarkable findings such as cellular crescents, global sclerosis or interstitial infiltration. By immunoperoxidase microscopy, fine granular deposits of C3d were identified only in the mesangium, and arteriolar C3 staining was seen in 31 of the 55 patients. In 38 of the 42 patients examined by electron microscopy, electron-dense deposits were identified in the mesangial matrix. These findings suggest that isolated C3d deposition is a new entity with benign features both clinically and pathologically.