A case of a severe factor XI deficiency in patient undergoing hemodialysis without the use of heparin.

Factor XI (FXI) deficiency is a rare hematologic disease, and shows a less severe bleeding tendency compared with what is generally observed in patients with hemophilia A and B. FXI has received a lot of attention in recent years as a new therapeutic target. Here, we present a case of 59-year-old male patient with chronic renal failure. The patient was found to have a markedly prolonged activated partial thromboplastin time (aPTT) during routine preoperative blood test before an arteriovenous fistula surgery. Finally, he was diagnosed with FXI deficiency. More than 6 months after the start of hemodialysis, no sign of blood clotting in the extracorporeal circuit has been observed. Of note, the patient did not receive any anticoagulant during hemodialysis, and he did not show any bleeding tendency even with aPTT more than 120 s and FXI activity below 3% of normal in a patient with renal failure. To our knowledge, this is the first case report to demonstrate FXI deficiency exhibiting anticoagulant effect equivalent to heparin in dialysis.