An hereditary deficiency in Factor XI can result in a lifelong bleeding disorder or go undetected.
Inheritance: autosomal recessive, with an increased frequency seen in Ashkenazi Jews.
Clinical findings:
(1) An affected patient may show a variable bleeding tendency that depends on the level of Factor XI present.
(1a) A patient with a minor factor deficiency may have a minor bleeding disorder.
(1b) A patient with a major factor deficiency may experience excessive bleeding.
(2) The bleeding may only be noted after significant trauma or surgery or dental extraction. Spontaneous bleeding does not occur.
(3) The bleeding may be worse after aspirin or if other coagulation deficiencies are present.
(4) Other family members may be affected, with both genders affected.
Bleeding sites:
(1) joint or muscle
(2) epistaxis
(3) soft tissue hemorrhage
(4) menorrhagia in a woman
Laboratory findings (assuming no factor replacement):
(1) prolonged aPTT
(2) normal PT and thrombin time
(3) decreased Factor XI activity by specific assay
(4) The assay for Factor XI may be falsely elevated if the blood sample is exposed to glass or if it has been frozen (false negative).
Differential diagnosis of a hereditary deficiency:
(1) Other hereditary coagulation factor deficiency
(2) von Willebrand's disease
(3) acquired factor XI inhibitor
