PB0226 - Bleeding and clotting in the same patient: A case of Factor XI deficiency and thrombosis.

Background: Factor XI (FXI) deficiency is a rare autosomal recessive inherited bleeding disorder with a higher prevalence among Ashkenazi Jews. There is a poor correlation between factor FXI deficiency and bleeding tendency. Bleeding, which occurs following trauma or surgery, is most prevalent in mucocutaneous tissues such as the nasopharynx and the genitourinary tract. The risk of venous thromboembolism (VTE) in FXI deficiency is reduced, with severe deficiency conferring a lower risk of VTE. The occurrence of bleeding and clotting in the same patient is rare.

Aims: To describe a case of bleeding and thrombosis in a patient with FXI deficiency.

Methods: A 76-year-old Jewish male was diagnosed with a right common femoral vein thrombosis as shown in Figure 1 and was treated with warfarin. A year later, he presented with a right neck of femur fracture following trauma. He was hospitalised and treated with a low molecular weight heparin (LMWH). He developed gastrointestinal and skin bleeding with supratherapeutic anti-factor Xa activity and a prolonged activated partial thromboplastin time (aPTT), which failed to clot but corrected with mixing studies.

Results: A review of his prior laboratory investigations in the referring hospital revealed multiple prolonged aPTTs, predating the thrombosis. Coagulation factor VIII and FIX levels were normal, with a low FXI level of 2 IU/dL as depicted in Table 1. The patient was diagnosed with a FXI deficiency, and a right hemiarthroplasty was performed under fresh frozen plasma cover. The surgery went well, with no bleeding. However, the patient developed a pulmonary embolus and demised post-surgery.

Conclusion(s): This instructive case highlights several noteworthy features. First, it emphasises the importance of investigating unexplained abnormal coagulation blood results. Secondly, low FXI levels and thrombosis are not mutually exclusive. Finally, FXI deficiency is heterogeneous in clinical presentation with a diagnosis made in this patient’s 7th decade of life.