Proliferative glomerulonephritis with monoclonal immunoglobulin G deposits in a young woman: A case report

BACKGROUND: Proliferative glomerulonephritis with monoclonal immunoglobulin G (IgG) deposits (PGNMID) is a newly recognized rare disease. The renal pathology is characterized by prominent manifestations of membranous hyperplasia, which are easy to misdiagnose. The clinical symptoms are severe. Massive proteinuria and hypoproteinemia are conspicuous, and most patients are accompanied by renal insufficiency and microscopic hematuria. CASE SUMMARY: A 27-year-old woman was admitted to a hospital for macroscopic hematuria and proteinuria 4 years prior, and renal biopsy in the hospital suggested moderate-to-severe mesangial proliferating glomerulonephritis (MsPGN). She had taken a glucocorticoid, cyclophosphamide, mycophenolate mofetil, and other treatments and achieved brief partial remission. Recently, the patient visited our hospital due to massive proteinuria. Repeated renal biopsy and re-evaluation of the first biopsy obtained 4 years previously revealed monoclonal immunoglobulin deposition in the glomeruli. A bone marrow examination was performed to exclude hematologic malignancy, and a diagnosis of PGNMID was established. The patient showed remission after four cycles of a bortezomib + cyclophosphamide + dexamethasone scheme. CONCLUSION: PGNMID is usually misdiagnosed as MsPGN or membranoproliferative glomerulonephritis. Although it often occurs in middle-aged and elderly individuals, it cannot be readily excluded in young people, even when serum immunofixation electrophoresis is negative. IgG subtype and light chain staining are necessary when this disease is highly suspected. An accurate diagnosis at the earliest stage may avoid the overuse of glucocorticoids and immunosuppressants.