[Refractory nephrotic syndrome].

In Japan, refractory nephrotic syndrome is defined as a pathological condition resistant to the treatment using corticosteroids and other immunosuppressive for 6 months or more. The Research Group on Progressive Renal Disease sponsored by the Ministry of Health Labor and Welfare of Japan reported that 10 to 12% of the cases with idiopathic nephrotic syndrome were classified into this type and that the most common cause in adults is idiopathic membranous nephropathy (40%) and the second is focal segmental glomerulosclerosis (20%). In these conditions, less than 10% progressed to end stage renal disease (ESRD) when urine protein decreased under 1 g/day by the treatment. Persistent proteinuria is not only a marker of irreversible glomerular lesions but also a risk factor for tubulointerstitial lesions, which plays a significant role in progression into ESRD.