ABSENCE OF MUTATIONS AT THE ACTIVATED PROTEIN-C CLEAVAGE SITES OF FACTOR-VIII IN 125 PATIENTS WITH VENOUS THROMBOSIS

Resistance to activated protein C (APC), caused by a mutation at amino acid position Arg(506) of the factor V gene, has recently been identi fied as the most prevalent genetic defect associated with venous throm bosis. Similarly to factor V, mutations at the cleavage sites of facto r VIII for APC may occur in patients with venous thrombosis. Here we h ave analysed 125 consecutive patients with incidental or recurrent ven ous thromboembolism for the presence of mutations at the cleavage site s for APC at amino acid positions Arg(336) and Arg(562) of factor VIII . Our findings indicate that mutations at these amino acid positions o f factor VIII do not occur in the patient group analysed.