Although CD40 expression by glomerular epithelial cells (GECs)/podocytes has been recently shown by several research groups [9, 14–17], little is known on its physiologic function in this cell-type, and on its involvement in the pathogenesis of podocytopathies, a distinct group of diseases characterized by a functional modification of renal permselectivity, with proteinuria and nephrotic syndrome as clinical hallmarks, and minimal or focal segmental glomerulosclerosis lesions (MCN or FSGS, respectively) as their pathology backgrounds. The gene discussed is CD40; the disease is focal segmental glomerulosclerosis.