Pulmonary embolism with factor XI deficiency.

A patient with factor XI deficiency had pulmonary embolism, although his factor XI assay was less than 1% of normal and his postoperative course was complicated by prolonged bleeding. Programs designed to prevent postoperative venous thrombosis should be carried out in factor XI-deficient patients, since the deficient state offers no protection from a pulmonary embolus. All surgical patients who are to receive low-dose heparin therapy as a part of such a program should be screened by means of preoperative determination of the partial thromboplastin time, to identify previously unsuspected bleeding disorders.