Background and objectives. Diffuse mesangial sclerosis (DMS) is a histologically distinct variant of nephrotic syndrome (NS) that is characterized by early onset and by progression to end-stage kidney disease (ESKD). Besides syndromic DMS, isolated (non-syndromic) DMS (IDMS) has been described. The etiology and pathogenesis of DMS is not understood. We recently identified by positional cloning recessive mutations in the gene PLCE1/NPHS3 as a novel cause of IDMS. We demonstrated a role of PLCE1 in glomerulogenesis. Mutations in two other genes WT1 and LAMB2 may also cause IDMS. We therefore determine in this study the relative frequency of mutations in PLCE1, WT1 or LAMB2 as the cause of IDMS in a worldwide cohort.