RESEARCH ARTICLE Removal of focal segmental glomerulosclerosis (FSGS) factor suPAR using CytoSorb Heiko Schenk 1 | Janina M€ uller-Deile 1 | Roland Schmitt 1 | Jan Hinrich Bräsen 2 | Hermann Haller 1 | Mario Schiffer 1 1 Department of Nephrology and Hypertension, Hannover Medical School, Hannover, Germany 2 Institute for Pathology, Hannover Medical School, Hannover, Germany Correspondence Heiko Schenk, Mario Schiffer, Department of Nephrology and Hypertension, Hannover Medical School, Hannover, Germany. Email: Schenk.Heiko@mh-hannover.de, Schiffer.Mario@mh-hannover.de Funding information The study was supported by institutional funds from the Department of Nephrology and Hypertension of Hannover Medical School. Treatment of primary focal segmental glomerulosclerosis (FSGS) and its recurrence after kidney transplantation associated with rapid deterioration of kidney function remains to be challenging despite advances in immunosuppressive therapy. The pres- ence of circulating factors has been postulated to be a pivotal player in the pathogenesis of FSGS, although suPAR and CLCF-1 have been identified as the most promising causative factors. The potential therapeutic effect of suPAR elimina- tion in an FSGS patient using CytoSorb, a hemoadsorption device that gained attention in the cytokine elimination in septic patients, was studied. Efficiency of total plasma exchange to remove suPAR was determined. CytoSorb hemoadsorption caused a 27.33% reduction of the suPAR level in a single treatment, whereas total plasma exchange showed a suPAR level reduction of 25.12% (n 5 3; 95% confidence interval, 0.2777-0.8090; P < 0.01), which may indicate therapeutic potential in the treatment of primary FSGS and its recurrence in a kidney transplant. KEYWORDS CytoSorb, FSGS, plasmapheresis, podocytes, podocyturia, suPAR 1 | INTRODUCTION Focal segmental glomerulosclerosis (FSGS) is one of the most prevalent glomerular diseases that frequently leads to end-stage renal disease in adults. The etiologic classification of FSGS is difficult partly because it is based not only on his- tological classification but also on known or postulated causes. FSGS can be classified as a group of various diseases that share common glomerular lesions and a disruption of the podocyte structure. Clinical presentation of idiopathic FSGS includes rapid onset of heavy proteinuria in a nephrotic range, severe hypoalbuminemia, and often the first symptom that is recognized by the patients, peripheral edema. Many patients remain refractory to treatment by steroids and immunosup- pressants such as cyclosporine as well as second line treat- ments with rituximab and mycophenolat mofetil (MMF), therefore, progressive renal impairment still occurs. End-stage renal disease caused by FSGS often leads to the necessity of renal replacement therapy by dialysis or kid- ney transplantation. In idiopathic or primary FSGS, the injury to the podocyte appears to be linked with one or sev- eral circulating factors. The early onset and high incidence of FSGS recurrence sometimes within minutes after transplanta- tion points toward the existence of a remaining factor that causes the podocytopathy in the transplanted kidney. A recurrence rate of 30–50% has been observed in transplants of patients with primary FSGS exceeding 80% if previous allograft loss due to recurrence is prevalent. 1,2 Additionally, if serum from patients suffering from primary FSGS is injected into rats, it leads to the onset of proteinuria. 3–5 Fur- thermore, it increases the permeability to albumin of isolated glomeruli in a rat model which underscores its pathophysio- logical role. 6 The presence of a transmittable factor is sup- ported by a fetus that developed proteinuria in the thirteenth week of gestation while the mother had histology proven FSGS and nephrotic syndrome. 7,8 . Taking these examples into account, the association of idiopathic FSGS with a circu- lating factor appears to be undisputable. The necessity to detect circulating factors that either directly or indirectly effect the onset of FSGS has been stated to be of high J Clin Apher. 2017;1–9. wileyonlinelibrary.com/journal/jca V C 2017 Wiley Periodicals, Inc. | 1 Received: 20 January 2017 | Revised: 14 March 2017 | Accepted: 15 March 2017 DOI: 10.1002/jca.21538