Prominent IgM Deposition in Glomerulus Is Associated with Severe Proteinuria and Reduced after Combined Treatment of Tonsillectomy with Steroid Pulse Therapy in Patients with IgA Nephropathy

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IgA nephropathy (IgAN) is characterized by mesangial deposition of IgA, C3, and often IgM. We examined the relationship among IgM deposition, clinical features, and renal outcome in IgAN patients who underwent combined treatment of tonsillectomy with steroid pulse therapy (Tx-SP). We retrospectively reviewed 73 IgAN patients treated with Tx-SP from March 2006 to March 2014. The patients were divided into those with moderate (2+) to severe (3+) mesangial IgM deposition (Prominent IgM-positive patients, P-Group) and those with negative (−) to faint (1+) deposition (the “Other” patients, O-Group). Using propensity scores to minimize confounding factors, 11 propensity score-matched patients with O-Group (mO-Group) were compared to 11 P-Group patients. The study outcome was defined as urinary protein grade by urine test strip before Tx-SP and one year after Tx-SP. P-Group patients exhibited an increased severity of proteinuria compared to O-Group (p=0.018) and mO-Group patients (p=0.009) before Tx-SP. After Tx-SP, proteinuria was significantly ameliorated in the P-Group, reaching the same severity recorded in the O-Group (p=0.007) and mO-Group (p=0.021). No significant differences were noted between P-Group and mO-Group in microhematuria, serum creatinine level, and histological severity. Prominent IgM deposition is associated with severe proteinuria in IgAN. However, Tx-SP induces a sufficient reduction in the severity of proteinuria in IgM-positive IgAN.