Clinical features and outcomes of IgA nephropathy with nephrotic syndrome.

BACKGROUND AND OBJECTIVES Nephrotic syndrome (NS) is a rare manifestation of IgA nephropathy (IgAN). Clinical characteristics and long-term outcomes of this condition have not yet been explored. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS A multicenter observational study was conducted between January 2000 and September 2010 in 1076 patients with biopsy-proven IgAN from four medical centers in Korea. The primary outcome was a doubling of the baseline serum creatinine concentration. RESULTS Of the 1076 patients, 100 (10.2%) presented with NS; complete remission (CR), partial remission (PR), and no response (NR) occurred in 48 (48%), 32 (32%), and 20 (20%) patients, respectively. During the median follow-up of 45.2 months, 24 patients (24%) in the NS group reached the primary endpoint compared with 63 (7.1%) in the non-NS group (P<0.001). The risk of reaching the primary endpoint was significantly higher in the PR (P=0.04) and NR groups (P<0.001) than in the CR group. Among patients with NS, 24 (24%) underwent spontaneous remission (SR). SR occurred more frequently in female patients and in patients with serum creatinine levels ≤1.2 mg/dl and a >50% decrease in proteinuria within 3 months after NS onset. None of the patients with SR reached the primary endpoint and they had fewer relapses during follow-up. CONCLUSIONS This study demonstrated that the prognosis of NS in IgAN was not favorable unless PR or CR was achieved. In addition, SR was more common than expected, particularly in patients with preserved kidney function and spontaneous decrease in proteinuria shortly after NS onset.