Background/objective: Products of heme oxygenase 1 (HO1) possess antithrombotic properties, and impairment of HO1 activity may contribute to thrombus formation. Transcriptional activity of long GT-repeat alleles in HO1 gene (HMOX1) is lower as compared with short alleles. We hypothesize that these long alleles are associated with decreased HO1 anticoagulant activity and, thus, an increased risk of thrombosis..
Design/methods: In a prospective cohort study, we followed 860 patients with a first VTE, and investigated the impact of a promoter GT-dinucleotid length polymorphism in HOMX1 on the risk of recurrent venous thromboembolism (VTE).
Results: Allele groups short (S), medium (M) and long (L) of the promoter GT-dinucleotide length polymorphism were distinguished. L-alleles, but not M- or S-alleles, were found to be more frequent among patients with recurrence. Heterozygous carriers of L-alleles had a two-fold higher relative risk of recurrence [(RR 2.2 (95% CI: 1.4-3.4)] as compared to wild type, which was independent of other thrombotic risk factors. At five years, the cumulative probability of recurrence was 18% (95% CI: 15%-22%) in patients without an L-allele compared to 32% (95% CI: 19%-46%) in patients heterozygous for the L-allele (P = .001).
Conclusion: Patients with first VTE and long GT-repeat alleles in HMOX1 have an increased risk of recurrence. Genetically determined alterations in HO1 function may represent a new pathomechanism in VTE.