title: Successful management of factor IX inhibitor-associated nephrotic syndrome in a hemophilia B patient.
abstract: BACKGROUND
  Nephrotic syndrome (NS) is a recognized complication of immune tolerance induction (ITI) therapy, a treatment strategy used to treat inhibitors in patients with hemophilia B receiving factor IX concentrate.
  
  
  METHODS
  We present a 4-year-old boy with hemophilia B and an inhibitor who underwent ITI, and developed NS 19 months into this therapy. A percutaneous renal biopsy was safely performed with factor IX (FIX) concentrate administration both preceding and following the procedure. The patient's inhibitor level had increased to 1.4-1.6 Bethesda Units just prior to the onset of proteinuria. Histology confirmed segmental membranous nephropathy (MGN). The patient was continued on FIX concentrate as ITI and also received 4 weekly doses of rituximab and ongoing immunosuppression with mycophenolate mofetil. This resulted in the complete resolution of his inhibitor and his NS. He continues with a modified ITI regimen and remains inhibitor-free without proteinuria >12 months post-biopsy.
  
  
  CONCLUSIONS
  Hemophilia B patients undergoing ITI should be regularly screened for NS. At first detection of proteinuria, with proper precautions, a percutaneous kidney biopsy can be performed safely in patients with low levels of inhibitor. Our patient had segmental MGN with complete remission of NS.
authors: University of Minnesota-Pediatric Nephrology, 2450 Riverside Avenue, Minneapolis, MN 55437, USA. pverghes@umn.edu.
authors: Priya
authors: P
authors: Verghese
authors: Stephen
authors: S
authors: Darrow
authors: Margaret H
authors: MH
authors: Kurth
authors: Robyn C
authors: RC
authors: Reed
authors: Youngki
authors: Y
authors: Kim
authors: Susan
authors: S
authors: Kearney
mesh_terms: D000906:Antibodies / Q000097:blood*; D058846:Antibodies, Monoclonal, Murine-Derived / Q000008:administration & dosage*; D001706:Biopsy; D002675:Child, Preschool; D003029:Coagulants / Q000009:adverse effects / Q000037:antagonists & inhibitors / Q000276:immunology*; D005164:Factor IX / Q000009:adverse effects / Q000037:antagonists & inhibitors / Q000276:immunology*; D015433:Glomerulonephritis, Membranous / Q000175:diagnosis / Q000276:immunology / Q000628:therapy*; D002836:Hemophilia B / Q000097:blood / Q000188:drug therapy* / Q000276:immunology; D006801:Humans; D007108:Immune Tolerance; D007166:Immunosuppressive Agents / Q000008:administration & dosage*; D008297:Male; D009173:Mycophenolic Acid / Q000008:administration & dosage / Q000031:analogs & derivatives*; D009404:Nephrotic Syndrome / Q000175:diagnosis / Q000276:immunology / Q000628:therapy*; D011507:Proteinuria / Q000276:immunology / Q000628:therapy; D000069283:Rituximab; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D000906:Antibodies; D058846:Antibodies, Monoclonal, Murine-Derived; D003029:Coagulants; D007166:Immunosuppressive Agents; D000069283:Rituximab; D005164:Factor IX; D009173:Mycophenolic Acid
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