Treatment of idiopathic focal segmental glomerulosclerosis: options in the event of resistance to corticosteroids and calcineurin inhibitors.

Half of patients with nephrotic syndrome caused by primary focal segmental glomerulosclerosis (FSGS) have resistance to treatment with steroids. In the case of corticosteroid resistance,  the best evidence-based option has classically been treatment with calcineurin inhibitors,  although recent studies indicate that mycophenolate may have similar efficacy. In patients with resistance to calcineurin inhibitors,  there is no option that allows the clinical course of the disease to be modified, and this is supported by appropriately designed clinical trials, although observational studies have suggested the potential usefulness of mycophenolate, sirolimus, rituximab, apheresis or high galactose doses as treatment options. In FSGS of idiopathic origin, resistant to steroids and calcineurin inhibitors, before taking the decision whether or not to test other immunosuppressive drugs, it might be appropriate to conduct a systematic analysis that considers: 1) evaluating whether the dose and duration of treatment with steroids and calcineurin inhibitors were suitable, 2) analysing the level of P-glycoprotein expression in lymphocytes, 3) performing a new renal biopsy if there is no electron microscopic study available for the first, 4) in young patients,  considering a genetic study to rule out the presence of the podocin variant pR229Q in combination with heterozygous mutations in NPHS2,  and 5) evaluating the seriousness and difficulty of managing the nephrotic syndrome and the likelihood of progressive loss of renal function. Currently, there are multiple study avenues that attempt to identify the pathogenic mechanisms that cause podocyte injury and there are also several studies underway to analyse the efficacy of drugs such as adalimumab, fresolimumab, rosiglitazone, ACTH (corticotropin) or galactose at high doses, whose preliminary results have generated expectations that require confirmation in larger-scale clinical studies.  In the future, it is possible that a better understanding of the pathogenic pathway or pathways that cause FSGS may allow differentiation between immunomodulable and non-immunomodulable forms,  however, this continues to be a challenge currently.