A rare case of proliferative glomerulonephritis with monoclonal IgG2 kappa deposit: a case report.

BACKGROUND: Proliferative glomerulonephritis with monoclonal immunoglobulin G (IgG) deposits (PGNMID) is a rare monoclonal gammopathy of renal significance with dense deposits of monoclonal immunoglobulin. CASE PRESENTATION: We report a 78-year-old Japanese male patient with mild proteinuria and lower extremity edema. Monoclonal immunoglobulin could not be identified in his serum or urine. Although his bone marrow biopsy was negative, renal biopsy found features of membranoproliferative glomerulonephritis (MPGN) with deposition of monoclonal IgG2 kappa. Electron microscopy examination revealed non-organized electron-dense deposits in the subepithelial, and subendothelial mesangial regions. Steroid monotherapy was performed after diagnosis of PGNMID but complete remission was not achieved. CONCLUSION: PGNMID with IgG3 kappa deposits is the most common in cases with the histological feature of MPGN. There are few cases of PGNMID with IgG2 kappa deposits exhibiting MPGN. This report describes a very rare case of PGNMID with the histological feature of MPGN.

Case report: increased single-nephron estimated glomerular filtration rate in an adult patient with low birth weight.

BACKGROUND: Low birth weight (LBW) is associated with end-stage kidney disease and hypertension and is considered to be a surrogate marker of low nephron number. Low nephron number is hypothesized to contribute to glomerular hyperfiltration that may cause kidney injury; however, this is not yet proven. Until now, the hyperfiltration in LBW patients has not been shown directly yet. CASE PRESENTATION: A 23-years-old female was referred with the persistent proteinuria and decreased renal function (estimated glomerular filtration rate by cystatin C (eGFRcys); 41.86 ml/min). She was a premature baby with low birth weight (704 g, 24 gestational weeks). Renal biopsy demonstrated focal segmental glomerulosclerosis (FSGS) of the perihilar variant with expanded glomerular diameter. We calculated the single-nephron estimated glomerular filtration rate (SN-eGFR) that was higher than that of the same age group in the healthy living kidney donors and speculated that glomerular hyperfiltration is a pathophysiological cause of FSGS. CONCLUSION: This is the first case of SN-eGFR measurement in a patient with LBW. The increased SN-eGFR in this case provides an important insight into the pathophysiological mechanisms of LBW for its progression to kidney disease.