Summary
To investigate whether the factor V Leiden mutation increases the risk of fatal pulmonary
emboli, we determined the presence of the factor V Leiden mutation in pathology material
from two series of autopsies of patients from the Leiden University Hospital, The
Netherlands. The first series consisted of consecutive autopsies in which pulmonary
emboli were mentioned in the autopsy report; most patients of this series had major
underlying disease. The second series consisted of autopsies in patients younger than
age 70 in which pulmonary emboli were the sole cause of death and no major acquired
risk factor for venous thrombosis was present. Extraction of DNA was done on newly
prepared tissue from archival paraffin blocks. In the first series, the presence of
factor V Leiden was determined in 44 patients, 1 of whom carried the mutation (2.3
percent; 95% confidence interval 0.06 to 12.0 percent). This prevalence is not different
from the general population prevalence in The Netherlands. In the second series, factor
V Leiden could be determined in 30 patients of whom 3 carried the mutation (10 percent;
95% confidence interval 2.1 to 26.5 percent), which would lead to a threefold relative
risk. A large number of patients with diverse psychiatric diagnoses was present in
the second series (eleven). We conclude that in the presence of severe illness, the
factor V Leiden mutation plays no additional role in the development of pulmonary
emboli. The relative risk of the very rare fatal pulmonary embolus that is the sole
cause of death might also be less than the relative risk for deep-vein thrombosis
in carriers of the factor V Leiden mutation.
