Alteration of C3 Nephritic Factor in a Patient with Membrano- proliferative Glomerulonephritis Type II

J. Seino, 2nd Department of Internal Medicine, Tohoku University School of Medicine, 1-1 Seiryo-Cho, Aoba-Ku, Sendai 980 (Japan) Dear Sir, C3-nephritic factor (C3NeF) is often found in patients with membranoprolifera-tive glomerulonephritis (MPGN) type II [1]. In plasma, low levels of C3, caused by activation of the alternative pathway of complement, are accompanied by relatively normal levels of Cl, C4, and C2 [2]. Performing immu-nohistological studies, C3 deposition is also frequently observed in the glomeruli. However, the relationship between C3NeF, hypo-complementemia, and immunological renal lesions is still controversial. We observed a case with MPGN type II who developed chronic renal failure and whose C3NeF level decreased and disappeared with progression of chronic renal failure and reappeared after starting hemodialy-sis. The relation between CH50/C3 and C3NeF levels was completely reciprocal during the clinical course of this patient. A 7-year-old girl presented with facial edema and oliguria 2 weeks after catching a common cold in 1975. Heavy proteinuria and slight microhematuria were pointed out by her doctor. There was no family history of any medical diseases. In 1977, a renal biopsy specimen was obtained because of a persistent proteinuria. She was diagnosed as having MPGN by light microscopy, showing lobular formation with mesangial and endocapillary proliferation in all glomeruli. However, the study by electron microscopy demonstrated no dense deposits in the glomerular basement membrane, but only lamellation of the lamina densa. In 1982, a second renal biopsy specimen was obtained because heavy proteinuria and nephrotic syndrome had continued. Electron microscopy revealed typical dense deposits of MPGN type II on the lamina densa in all glomerular basement membranes [3]. A detailed complement profile of this patient was first studied in 1983. Then renal function tests revealed values within normal ranges: serum creatinine 0.6 mg/dl, blood urea nitrogen 11 mg/dl, and creatinine clearance (C„) 96 ml/min. Complement assays showed extremely reduced CH5Π (15 U/ml) and C3 (10 mg/dl) levels (fig. 1), a high titer of C3d, and a normal C4 titer (34 mg/dl).