Molekularne osnove trombofilije

Abstract

Trombofilija nastaje kao rezultat kompleksne interakcije između negenetičkih i genetičkih faktora rizika koji hemostaznu ravnotežu pomeraju u smeru hiperkoagulacije i dovode do pojave tromboze. Veoma značajan faktor rizika za nastanak trombofilije je deficijencija inhibitora koagulacije: antitrombina, proteina C ili proteina S. Veliki korak u razumevanju genetičke osnove i molekularne dijagnostike trombofilije napravljen je otkrićem rezistencije na aktivirani protein C i faktor V Leiden mutacije. Ubrzo je otkrivena i varijanta u 3'-nekodirajucem regionu gena za faktor II (FII G20210A), za koju je pokazano da dovodi do povišene koncentracije protrombina u plazmi. Ove dve genske varijante su najučestaliji genetički faktori rizika za nastanak trombofilije. Nedavno je opisana nova mutacija u genu za protrombin (c.1787G gt T) za koju je pokazano da dovodi do rezistencije na antitrombin, odnosno do smanjene mogućnosti inaktivacije mutiranog trombina od strane antitrombina, sto predstavlja novi mehanizam za nastanak trombofilije. U toku poslednjih decenija, opisan je veliki broj genetičkih faktora rizika za nastanak trombofilije, uključuju}i one koji dovode do: nedostatka inhibitora koagulacije, povećanog nivoa ili smanjene inaktivacije koagulacionih faktora ili defekata sistema za fibrinolizu. Međutim, većina njih nije od dijagnostičke važnosti zbog njihovog malog ili još uvek nepoznatog uticaja na etiologiju trombofilije. Primena novih tehnologija koje omogućavaju analizu velikog broja gena kod jednog pacijenta otvoriće mogućnost individualnog utvrđivanja genetičkih faktora rizika, samim tim i adekvatan terapeutski pristup.

Thrombophilia is a multifactorial disorder, involving both genetic and acquired risk factors that affect the balance between procoagulant and anticoagulant factors and lead to increased thrombotic tendency. The severe forms of thrombophilia are caused by a deficiency of natural anticoagulants: antithrombin, protein C and protein S. The advances in DNA technology played an important role in the identification of the exact nature of these deficiencies and opened up new possibilities in genetic research and molecular diagnostics of thrombophilia. The major breakthrough came with the discovery of activated protein C resistance and the Factor V Leiden gene mutation. Shortly afterwards, a variant in the 3' untranslated region of the Factor II gene (FII G20210A) associated with an increased concentration of Factor II in plasma was described. These two gene variants represent the most common thrombophilic genetic risk factors. Recently, a novel prothrombin mutation (c.1787G gt T) was identified in a Japanese family with juvenile thrombosis. This mutation leads to impaired inhibition of mutant thrombin by antithrombin, proposing a new mechanism of thrombophilia named resistance to antithrombin. In the last decade, several prothrombotic genetic risk factors have been described, including gene variants associated with defects of natural coagulation inhibitors, increased levels of coagulation factors or their impaired inhibition and defects of the fibrinolytic system. However, most of them are not of diagnostic value, due to their minor or unknown impact on the thrombotic risk. Large-scale DNA analysis systems are now becoming available, opening a new era in the genetic studies of the molecular basis of thrombophilia.