Heerlen polymorphism associated with type III protein S deficiency and factor V Leiden mutation in a Polish patient with deep vein thrombosis.

Protein S is one of the major natural anticoagulants. A missense serine 501 to proline (S501P) Heerlen polymorphism is associated with reduced levels of free protein S. Heerlen polymorphism, especially when combined with other thrombophilia risk factors, can lead to thromboembolic complications. To our knowledge, we report here the first Polish case associated with heterozygous Heerlen polymorphism resulting in type III protein S deficiency, detected in a 50-year-old man with several thrombotic episodes of deep and superficial veins and a highly positive thrombotic family history. The patient also had factor V Leiden mutation and persistently elevated anticardiolipin antibodies. It seems that increased risk of thrombotic complications could be explained in the patient by a synergy between the effects of Heerlen polymorphism, factor V Leiden heterozygous status and antiphospholipid syndrome.