Pta (Factor Xi) Deficiency and Prolonged Bleeding Time

A 23‐year‐old man with an inherited haemorrhagic diathesis characterized by factor XI deficiency and prolonged Ivy bleeding time is reported. The platelets aggregated normally with ADP, but the disaggregation of platelets was rapid. The release of ADP induced by kaolin or adrenaline was defective, as was the release of PF‐3 induced by kaolin. Thrombopathy was therefore diagnosed and the prolonged bleeding time was attributed to a platelet defect. Administration of fresh platelets shortened the bleeding time. The level of factor XI was 1–5%. Although the administration of platelet‐poor plasma corrected the coagulation defect, it had no effect on bleeding time.