Mesangial isolated C3 deposition in patients with recurrent or persistent hematuria

We reviewed 222 renal biopsies performed on patients with nonurologic hematuria alone or hematuria and proteinuria. This review revealed 31 patients who presented minor glomerular abnormalities with granular mesangial C3 deposition without any immunoglobulin or other complement component deposits. These patients presented with gross hematuria in five cases, microscopic hematuria alone in 12 cases, and proteinuria and microscopic hematuria in 14 cases. Light microscopy disclosed a segmentally increased mesangial matrix, sometimes associated with a segmental and focal mesangial hypercellularity. Focal tubulointerstitial and arteriolar lesions occurred in seven cases. In all cases, immunofluorescence showed diffuse granular mesangial deposition of C3. However, the deposits were not observed along the glomerular and tubular basement membranes. We should point out the high frequency of arteriolar C3 deposits (27 of 31). They were either isolated or associated with IgM or other complement components. Using electron microscopy, an increase of mesangial matrix and/or a proliferation of mesangial cells was observed. In two cases, electron-dense deposits were present in the mesangium. Glomerular basement membranes were normal in all but five cases, where they appeared segmentally thickened. After a 3-year follow-up study the clinical features remained unchanged.