[Management of severe idiopathic nephrotic syndrome in children].

Severe forms of the nephrotic syndrome are, by definition, steroid-resistant or strongly steroid-dependent. Steroid-resistant forms have two causes. The first is T and B lymphocyte dysfunction, which may result in the production of a lymphokine which increases the permeability of the glomerular filtration barrier. The second is mutation of genes that encode proteins involved in establishing and maintaining the glomerular filtration barrier. Mycophenolate mofetil and rituximab are effective new treatments for severe steroid-dependent nephrotic syndromes. The beneficial effect of cyclosporine on proteinuria may result from stabilization of the actin cytoskeleton in podocytes.