A MUTATION IN THE THROMBOMODULIN GENE, (127)G TO A CODING FOR ALA25THR, AND THE RISK OF MYOCARDIAL-INFARCTION IN MEN

Thrombomodulin is an endothelial cell surface receptor that transforms the procoagulant thrombin into an anticoagulant. A mutation in the th rombomodulin gene is a potential risk factor for venous and arterial t hrombosis. We screened a region within the coding sequence of the thro mbomodulin gene by single-strand conformation polymorphism analysis (S SCP) in a pilot study of 104 patients with myocardial infarction and 1 04 age, sex and race matched controls. We identified a (127)G to A mut ation in the gene, which predicts an Ala25Thr substitution, in 2 out o f 104 patients (1 man and 1 woman) with myocardial infarction but in n o controls. We assessed the risk of myocardial infarction associated w ith the mutation in a larger ''Study of Myocardial Infarctions Leiden' ' (SMILE). Among 560 men with a first myocardial infarction before the age of 70, 12 were carriers of the Ala25Thr substitution. In a contro l group of 646 men, frequency-matched for age, seven were carriers of the Ala25Thr substitution. The allelic frequencies were 1.07% among pa tients and 0.54% among controls suggesting risk associated with the mu tation [odds ratio (OR) 2.0, 95% confidence interval (CI) 0.8-5.1]. In patients aged below 50, the predicted risk was almost seven times inc reased (OR 6.5, CI 0.8-54.2). In the presence of additional risk facto rs, such as smoking and a metabolic risk factor, the predicted risk in creased to 9-fold (OR 8.8, CI 1.8-42.2) and 4-fold (OR 4.4, CI 0.9-21. 3), respectively. While not conclusive, these results strongly suggest that the Ala25Thr substitution is a risk factor for myocardial infarc tion, especially in young men, and when in the presence of additional risk factors.