Circulating permeability factors such as the soluble urokinase receptor (suPAR) [20, 21] and autoantibodies directed against actin, adenosine triphosphate synthase, angiotensin II type 1 receptor, nephrin (NPHS1), protein tyrosine phosphatase receptor type O (PTPRO), and Thy1 have been implicated in the pathogenesis of FSGS recurrence [15, 22–24]. Here, PTPRO is linked to focal segmental glomerulosclerosis.