Severe venous thromboembolism in a young man with Klinefelter’s syndrome and heterozygosis for both G20210A prothrombin and factor V Leiden mutations.

Klinefelter's syndrome is the most common cause of primary testicular failure, resulting in impairment of both spermatogenesis and testosterone production. It is a chromosomal disorder characterized by small, firm testes, azoospermia, gynecomastia, varying degrees of eunuchoidism and testosterone deficiency with elevated gonadotropin plasma levels. In Klinefelter's syndrome there is an increase of certain systemic diseases including venous thromboembolism. An increased thromboembolic risk in hypogonadic men has been explained with hypofibrinolysis due to androgen deficiency. Only two cases have been reported about the association between Klinefelter's syndrome and well-known congenital or acquired thrombophilias. We report the case of a 39-year-old patient with Klinefelter's syndrome who underwent severe deep venous thrombosis with pulmonary embolism, in the absence of any circumstantial triggering event. Further examinations also showed a double heterozygosis for G20210A prothrombin and factor V Leiden mutations. This case suggests that the increased thromboembolic risk, reported in Klinefelter's syndrome, can be worsened by the co-existence of one or more well-known thrombophilic conditions, as shown by the relatively young age of the patient. More studies are needed to clearly understand the pathogenesis of venous thromboembolism in males affected by Klinefelter's syndrome.