[Nephrotic syndrome in childhood].

Minimal change nephrosis, the main pediatric form of idiopathic nephrotic syndrome is usually a benign condition responsive to standard steroid treatment. However, relapses occur frequently leading to secondary steroid resistance in a small proportion of cases. Steroid resistant nephrotic syndrome presents mainly as focal segmental glomerulosclerosis. It represents about 8-10% of cases of pediatric idiopathic nephrotic syndrome. The prognosis of focal segmental glomerulosclerosis is bad, with the majority of cases evolving to terminal renal insufficiency within several years. Among the causes of idiopathic nephrotic syndrome are changes of cellular immunity, circulating plasma factors not fully identified yet and mutations of podocyte proteins. Podocyte mutations are responsible for the development of about one third of cases steroid resistant focal segmental glomerulosclerosis. Treatment of idiopathic nephrotic syndrome is determined by international guidelines. If initial steroid treatment is followed by multiple relapses, levamisole, cyclophosphamide and finally cyclosporine-A are used stepwise. In the case of steroid resistance podocyte mutations should be evaluated. If mutated, aggressive steroid treatment is contraindicated. Cases without mutations are candidates for an intensified steroid therapy and cyclosporine-A. Recurrence of focal segmental glomerulosclerosis following transplantation can be suspected in patients without podocyte mutations. Due to the crucial role of the presence of mutations in focal segmental glomerulosclerosis, genetic evaluation before aggressive immunosuppression and preceding transplantation should be introduced. Supportive treatment of idiopathic nephrotic syndrome consists of fluid and salt restriction, protein intake tailored to the protein losses, prevention of thrombosis and infection, and -mainly in steroid resistant cases--measures to prevent of premature atherosclerosis and deterioration of kidney function.