CLCF1 and others have been identified as potential circulating permeability factors in the plasma of patients with focal segmental glomerulosclerosis (FSGS), a clinicopathological syndrome characterized by nephrotic-range proteinuria with a high incidence of progression to end-stage renal disease [78,79,80,81]. Here, CLCF1 is linked to focal segmental glomerulosclerosis.