[Prominent subepithelial deposits detected on 2nd renal biopsy in a boy with membranoproliferative glomerulonephritis type I: a case report].

The first renal biopsy of a 7-year-old boy with microscopic hematuria, hypocomplementemia (CH50 20 U/ml, C3 33 mg/dl, C4 13 mg/dl) and otherwise normal renal function revealed lobular, but not diffuse, expansion of glomerular mesangial areas showing mild to marked mesangial cell proliferation and thickening of the capillary walls with double contours as seen on light microscopic examination. Granular C3 deposition along the capillary wall and in the mesangium was observed on immunofluorescent microscopy. Further, electron microscopy showed subendothelial dense deposits and circumferential mesangial interposition. Thus, he was diagnosed as membranoproliferative glomerulonephritis (MPGN) type I. Thereafter, high-dose, alternate-day administration of prednisolone was started. A few months after treatment, microscopic hematuria disappeared and hypocomplementemia improved. The second renal biopsy at 11 years of age showed markedly decreased mesangial cell proliferation and subendothelial dense deposits. However, C3 deposition still persisted and subepithelial dense deposits had increased in number prominently at this time. Whether MPGN type III is a distinct disease entity or a variant of MPGN type I has not yet been established. The morphological changes in this reported case might justify the notion that MPGN type III is a variant form of MPGN type I.