Pediatric idiopathic nephrotic syndrome: treatment strategies in steroid dependent and steroid resistant forms.

Idiopathic nephrotic syndrome (INS) is defined as massive proteinuria and hypoalbuminemia associated with dyslipidemia and generalized oedema in most cases. It is thought to be due to a plasma factor of immunologic origin. Most cases are steroid responsive. However, a considerable proportion of children run a steroid dependent course. Calcineurin inhibitors and alkylating agents have been classical treatment strategies for such cases, but specific toxicity limits the use of these drugs. Mycophenolate mofetil (MMF) is an inhibitor of inosine monophosphate dehydrogenase and thus de novo purine synthesis. Several uncontrolled clinical trials have demonstrated the efficacy of MMF in steroid dependent NS with or without prior use of CyP and in children with nephrotoxicity due to prolonged CyA treatment. Non-compliance to steroid therapy can be responsible for multiple relapses and may be misinterpreted as steroid dependency and may therefore lead to unjustified increase of immunosuppressive treatment. Triamcinolone acetonide, a long acting steroid for intramuscular injection, can replace the usual oral prednisone treatment if non-compliance is suspected. Whereas the treatment of the primary course of INS is well established, steroid dependent and steroid resistant forms are still a challenge for pediatric nephrologists. Both under-treatment with multiple relapses with disease or steroid associated morbidity on the one hand and over-treatment with specific side effects of immunosuppressive drugs may have severe consequences for the patients.