Summary

Factor XI (FXI) deficiency is an autosomal disorder which manifests as bleeding of varying severity. While homozygotes typically experience more dramatic bleeding symptoms, heterozygotes may experience clinically significant bleeding following surgical procedures or trauma, and therefore the condition is not purely recessive. The clinical significance of FXI deficiency is complicated in that FXI levels do not correlate well with bleeding severity, and in fact the bleeding risk is variable even for an individual in response to different haemostatic challenges. We present the case of a 74-year-old man of Ashkenazi Jewish heritage with a family and personal history of bleeding during surgical procedures, who presented with excessive bleeding following total thyroidectomy. He was found to have a FXI level of 52% (low normal). Genetic testing revealed that he was heterozygous for the c.403G>T mutation. This case demonstrates successful work-up and perioperative management of a patient with FXI deficiency.