Unique Case of Brothers with Moderate Factor XI Deficiency and One with Severe Bleeding After Surgery

Abstract

Factor XI is the only contact factor whose de ficiency may result in a bleeding diathesis. This case re port describes two brothers with similar moderate factor XI deficiency (41% and 45%), but one brother had severe bleeding during invasive procedures whereas the other brother undergoing the same surgical procedure had no excessive bleeding. The bleeding in the first brother con tinued despite adequate factor XI levels; however, it was stopped only after EACA therapy. Also discussed is the importance of a sensitive aPTT reagent to the various factors and the role of the aPTT in predicting potential bleeding, since a normal aPTT was obtained prior to the first surgery. This case demonstrates that major bleeding can occur in heterozygous factor XI deficiency and the patient must be considered 'at risk' for potential bleeding and should be treated accordingly.