[Combined antithrombin deficiency and factor VLeiden in a Danish family]

Factor VLeiden (FVL) and antithrombin (AT) deficiency are both known genetic risk factors for venous thromboembolism (VTE). The combination is rare and leads to significantly increased risk for VTE. In this case we present a 22-year-old woman with VTE while treated with oral contraceptives. Laboratory investigation of the patient and her relatives showed co-segregation of FVL and AT deficiency. This is the first Danish family reported with co-segregated FVL and AT deficiency, and this clarifies the importance for thorough laboratory screening of patients presenting VTE while treated with oral contraceptives.