ABSTRACT
Factor XI deficiency is an extremely rare disease presenting no clinical symptoms, unless there is an inducing reason such as trauma or surgery. Normally, factor levels are in the range of 70–150 U dL-1 in healthy subjects. Although no clinical symptoms are seen, only high levels of aPTT can be found. Once a prolongation is detected in aPTT, factor XI deficiency should be suspected and factor levels should be analysed. With careful preoperative preparations in factor-deficient people, preoperative and postoperative complications can be decreased. In this case report, management of anaesthesia during total hip arthroplasty of a patient with factor XI deficiency is presented.