[Therapeutic apheresis in idiopathic nephrotic syndrome]

Idiopathic nephrotic syndrome (INS) is characterized by diffuse foot process effacement on electron microscopy and minimal changes (called minimal change nephropathy [MCN]), focal segmental glomerular sclerosis (FSGS), or the mesangial variant with proliferation on light microscopy. No evidence of immune deposits is seen. MCN is the most common form of INS in children and is sensitive to corticosteroid therapy in 90% of cases. FSGS accounts for 20-30% of biopsy-proven glomerulopathies in adult patients. Fifty percent of drug-resistant patients develop terminal renal failure in 6-8 years. Moreover, FSGS reappears in 15-50% of cases after the first transplant and in a higher percentage after the second graft. Genetic forms of INS, with mutation of the NPHS1 and NPHS2 genes encoding nephrin and podocin, are mostly steroid resistant and very rarely recur in the transplant. On the basis of any clinical pattern they are indistinguishable from idiopathic forms. Sera from patients with FSGS may contain some proteinuric or permeability factors (PFs), which have been partially identified and are predictive of recurrence in kidney grafts. Removal of PFs by means of plasmapheresis or plasma immunoadsorption by protein A or LDL apheresis has been associated with proteinuria reduction in cases of FSGS both of native and transplanted kidneys, in small series or cohort studies described by many authors. In this review of the main studies we will analyze the results of the apheretic treatments and the role of some clinical, serological and histological parameters in determining the outcome of patients.