Summary
To further elucidate the debated role of hereditary FXII deficiency as a thrombophilic
risk factor this follow-up study on 65 subjects out of 12 Swiss families was undertaken
(follow-up: 6 yrs). Fifteen severely FXII deficient subjects (FXII:C < 1%), 35 partially
FXII deficient subjects (FXII:C ≥ 1-59%), 10 with normal FXII values (FXII:C ≥ 70%),
and 5 non-classifiable subjects (FXII:C ≥ 60-69%) were reevaluated. Eight subjects
(4 severely and 3 partially FXII deficient, 1 non-classifiable) were newly enrolled.
Four instances of deep vein thrombosis, one superficial vein thrombosis and one myocardial
infarction were noted in 2 out of 19 severely FXII deficient subjects during a total
life-time period of 866.6 patient-years. In 38 partially FXII deficient subjects (1862.8
patient-years) one ischemic cerebrovascular stroke and one superficial vein thrombosis
were recorded in 2 individuals. The 10 subjects with normal FXII values (498.2 patient-years)
remained thrombosis-free. One superficial vein thrombosis occurred in an unclassifiable
woman. None of the 3 different FXII gene defects revealed in our patients was specifically
associated with thromboembolic complications. Kaplan-Meier analysis of thrombosis-free
survival suggests that hereditary partial (and probably severe) FXII deficiency does
not constitute a thrombophilic condition.
Keywords
Factor XII deficiency - thromboembolic disease - factor XII gene mutations - thrombophilia