A case of proliferative glomerulonephritis with monoclonal IgG deposits (PGNMID) that responded favorably to steroid therapy.

Proliferative glomerulonephritis with monoclonal immunoglobulin deposits (PGNMID) generally has a poor prognosis and the consensus is that it needs to be treated with clone-directed therapy. However, the prognosis of PGNMID is heterogenous and some cases have been successfully treated using other therapeutic strategies. We herein report a case of PGNMID that responded favorably to steroids without clone-directed therapy. An 18-year-old woman was referred to a nephrologist with proteinuria detected in an annual health check-up. Over a 3-year period, the concentration of creatinine (Cr) increased from 0.76 to 1.00 mg/dL and proteinuria from 0.35 to 1.9 g/g Cr. Monoclonal gammopathies were not detected in her serum or urine. Based on the findings of kidney biopsy at the age of 21 years, the patient was diagnosed with proliferative glomerulonephritis with monoclonal IgG1-kappa deposits. The histological feature was mesangial proliferative glomerulonephritis with advanced glomerulosclerosis, which is a rare presentation of PGNMID. Intravenous methylprednisolone pulse therapy was initiated, followed by oral prednisolone at a dose of 30 mg daily. One year later, a second kidney biopsy revealed a significant decrease in mesangial deposits of IgG1-kappa. Prednisolone was gradually tapered and discontinued 2 years after the first kidney biopsy. At the time of prednisolone withdrawal, urinalysis showed proteinuria of 0.2 g/g Cr without hematuria. Kidney function remained stable throughout the treatment period.