Summary
Reduced fibrinolytic capacity due to increased plasminogen activator inhibitor-1 (PAI-1)
activity in plasma is a common finding in patients with coronary heart disease or
venous thromboembolism, although its clinical significance is debated. Recently, a
dimorphism in the PAI-1 promoter (4G-5G) has been reported and homozygosity for the
4G allele is associated with increased transcription and higher PAI-1 levels. Homozygous
4G genotype has been suggested to be a risk factor for myocardial infarction. In the
present study, the 4G-5G dimorphism was determined in 349 individuals from 21 thrombophilic
families with hereditary protein S deficiency and in 140 unrelated healthy controls.
Among the 143 protein S deficient individuals, there was no relationship between deep
or superficial venous thrombosis and the PAI-1 dimorphism. However, 26% (12/46) of
individuals having protein S deficiency combined with homozygosity for the 4G allele
had suffered pulmonary embolism as compared to 7% (7/97) of protein S deficient individuals
carrying at least one 5G allele (p = 0.0019). In protein S deficient individuals,
arterial thrombosis was found to be associated with smoking and 4G homozygosity. No
association was found between the PAI-1 dimorphism and arterial or venous thromboembolism
in family members without protein S deficiency. In conclusion, the PAI-1 genotype
affects the phenotypic expression of thrombophilia in protein S deficient individuals.