Outcomes of primary nephrotic syndrome in elderly Japanese: retrospective analysis of the Japan Renal Biopsy Registry (J-RBR).

BACKGROUND AND OBJECTIVES: There are very little data available regarding nephrotic syndrome (NS) in elderly (aged ≥65 years) Japanese. The aim of this study was to examine the causes and outcomes of NS in elderly patients who underwent renal biopsies between 2007 and 2010.

DESIGN, SETTING, PARTICIPANTS, AND MEASUREMENTS: From July 2007 to June 2010, all of the elderly (aged ≥65 years) Japanese primary NS patients who underwent native renal biopsies and were registered in the Japan renal biopsy registry (J-RBR; 438 patients including 226 males and 212 females) were identified. From this cohort, 61 patients [28 males and 33 females including 29, 19, 6, 4, and 3 patients with membranous nephropathy (MN), minimal change nephrotic syndrome (MCNS), focal segmental glomerulosclerosis (FSGS), membranoproliferative glomerulonephritis (MPGN), and other conditions, respectively] were registered from the representative multi-centers over all districts of Japan, and analyzed retrospectively. The treatment outcome was assessed using proteinuria-based criteria; i.e., complete remission (CR) was defined as urinary protein level of <0.3 g/day or g/g Cr, and incomplete remission type I (ICR-I) was defined as urinary protein level of <1.0-0.3 g/day or g/g Cr, and renal dysfunction was defined as a serum creatinine (Cr) level of 1.5 times the baseline level.

RESULTS: In this elderly primary NS cohort, MN was the most common histological type of NS (54.8 %), followed by MCNS (19.4 %), FSGS (17.4 %), and MPGN (8.4 %). Of the patients with MN, MCNS, or FSGS, immunosuppressive therapy involving oral prednisolone was performed in 25 MN patients (86.2 %), 18 MCNS patients (94.7 %), and all 6 FSGS patients (100 %). CR was achieved in all 19 (100 %) MCNS patients. In addition, CR and ICR-I were achieved in 16 (55.2 %) and 18 (62.1 %) MN patients and 4 (66.7 %) and 5 (83.3 %) FSGS patients, respectively. There were significant differences in the median time to CR among the MCNS, FSGS, and MN patients (median: 26 vs. 271 vs. 461 days, respectively, p < 0.001), and between the elderly (65-74 years, n = 7) and very elderly (aged ≥75 years, n = 12) MCNS patients (7 vs. 22 days, p = 0.037). Relapse occurred in two (6.9 %) of the MN and nine (47.4 %) of the MCNS patients. Renal dysfunction was observed in five (7.2 %) of the MN patients. Serious complications developed in eight (14.8 %) patients, i.e., two (3.7 %) patients died, four (7.4 %, including three MCNS patients) were hospitalized due to infectious disease, and two (3.7 %) developed malignancies. The initiation of diabetic therapy was necessary in 14 of the 61 patients (23.0 %) with much higher initial steroid dosage.

CONCLUSION: Renal biopsy is a valuable diagnostic tool for elderly Japanese NS patients. In this study, most of elderly primary NS patients respond to immunosuppressive therapy with favorable clinical outcomes. On the other hand, infectious disease is a harmful complication among elderly NS patients, especially those with MCNS. In future, modified clinical guidelines for elderly NS patients should be developed.