Intermediate type of primary glomerulonephritis between mesangial proliferative and membranoproliferative glomerulonephritis

Ten patients with primary mesangial proliferative glomerulonephritis (Mes PGN) with mild, irregular but distinct thickening of glomerular capillary walls observed by the light microscopy were studied. Silver staining revealed mesangial interposition and spike formation as well as apparent but not severe mesangial proliferation in all patients, but none of them showed lobular formation of glomerular tufts. Mesangial interposition were estimated as circumferential and diffuse similar to membranoproliferative glomerulonephritis (MPGN) type III in two patients, but in the other eight the interposition was only partial, so that the diagnosis of MPGN was considered to be improper for them. Electron microscopic examination, performed in seven patients, revealed mild to moderate deposition of subepithelial, subendothelial and mesangial dense deposits in almost equal severity. However, the immunofluorescence study for immunoglobulins (Ig) and C3 were rather predominant in the capillary wall than in the mesangial area and predominance was found in IgG in seven and in C3 in three patients. Their initial symptoms were acute nephritic syndrome (1), edema (1) and chance proteinuria (8). Their initial urinary protein was rather prominent compared to individual mesangial proliferation. Nephrotic syndrome appeareed in three patients in their clinical course but did not last longer than 6 months. None of them showed persistent hypocomplementemia. During the follow-up period, which ranged from 14 to 121, with a mean of 56 months, only one had fallen into chronic renal failure requiring regular hemodialysis after a 22 year clinical course and seven patients have kept normal renal function of glomerular filtration rate greater than 80 ml/min. Mild to moderate proteinuria has persisted in eight patients but eventually none remained in nephrotic state and proteinuria disappeared in two patients. These results strongly suggest that there exists an intermediate type of glomerulone phritis between MesPGN and MPGN from both clinical and pathological points of view.