Steroid-sensitive recurrent mesangial proliferative glomerulonephritis with monoclonal IgG deposits.

Proliferative glomerulonephritis with monoclonal immunoglobulin G (IgG) deposits (PGNMID) is a rare kidney disease. The predominant pathological finding of PGNMID is the presence of monoclonal Ig deposits on the glomerular basement membrane (GBM). However, there is some variation in deposition pattern in this kidney disease. We report a case of steroid-sensitive recurrent mesangial proliferative type of PGNMID. A 40-year-old female noticed lower leg pitting edema and polyuria. Approximately 10 days prior to the first clinic visit, she was diagnosed with nephrotic syndrome based on the laboratory data of urine and blood. Immunological and hematological examination revealed no abnormality. However, kidney biopsy specimens showed mild mesangial cell proliferation and mesangial matrix accumulation on light microscopic findings. Regarding immunofluorescence staining, granular deposits of IgG, C1q, and β1c were observed on GBM and mesangial area. Granular deposits of IgG3 and λ were also observed on GBM and mesangial area. Moreover, negative results were obtained for the phospholipase A2 receptor antibody and thrombospondin type-1 domain-containing 7A. Electron microscopy revealed highly electron dense deposits mainly in the mesangial region. Kidney biopsy showed mesangial proliferative glomerulonephritis characterized by monoclonal Ig deposition of IgG3/λ. Steroid therapy was initiated, and complete remission was achieved on day 36. After the discontinuation of steroid therapy, proteinuria recurred and second kidney biopsy findings were almost similar to the first biopsy. However, complete remission was achieved with steroid therapy. This is a rare recurrent case of steroid-sensitive PGNMID. The pathological feature of this case was mesangial proliferative glomerulonephritis with Ig deposition of IgG3/λ.