FACTOR-XI DEFICIENCY - DO PATIENTS WITH A BLEEDING TENDENCY HAVE OTHER HEMOSTATIC DEFECTS

It is well known that the extent of bleeding in patients with a defici ency of factor XI does not parallel the residual factor activity There fore, additional hemostatic aspects must be taken into consideration. 27 patients of 18 different families - 6 with severe (FXI <0.01 to 0.0 9 U/ml) and 21 with moderate (FXI 0.20 to 0.52 U/ml) factor XI deficie ncy - were reinvestigated regarding hemostasis including bleeding time and platelet function. 16 had an enhanced bleeding tendency, while th e others - including 3 with severe FXI deficiency of <0.01 U/ml - neve r suffered from bleeding complications despite delicate surgery in som e. All 16 of the symptomatic patients had, besides the reduction of fa ctor XI activity to various extents, an additional hemostatic defect: 3 had a moderate alpha/delta storage pool defect of the platelets, 11 a platelet anomaly mainly characterized by reduced ADP aggregation and 2 an isolated prolonged bleeding time of unknown cause. Synthesis of platelet thromboxane was unimpaired in all patients as tested by forma tion of malondialdehyde after stimulation with hs-ethyl maleimide. Hen ce, in patients with a known factor XI deficiency diagnostic and proph ylactic measures before surgery should concentrate on such additional findings. Preoperative administration of desmopressin, and not replace ment of factor XI, will be the treatment of choice in these cases.