RECURRENT VENOUS THROMBOEMBOLIC DISEASE AND FACTOR-XI CONCENTRATE IN A PATIENT WITH SEVERE FACTOR-XI DEFICIENCY, CHRONIC MYELOMONOCYTIC LEUKEMIA, FACTOR-V-LEIDEN AND HETEROZYGOUS PLASMINOGEN DEFICIENCY

There are increasing concerns about the potential thrombogenic risks a ssociated with the use of factor XI concentrates. We describe the case of a 49 year-old man with chronic myelomonocytic leukaemia and severe factor XI deficiency (< 1 u/dl), in whom the use of factor XI concent rate appeared to be associated with the development of venous thromboe mbolic disease. Subsequent investigations revealed the presence of bot h the factor V Leiden abnormality and heterozygous plasminogen deficie ncy. This case highlights the risks associated with the use of factor XI concentrates and suggests that these risks may be further increased in patients with an inherited or acquired prothrombotic abnormality o r an underlying malignancy. Prothrombotic screening of patients with s evere factor XI deficiency may be indicated particularly in younger pa tients in whom treatment with factor XI concentrates is a possibility.