Congenital Causes of Venous Thrombosis—A Classification System FREE

Some people are born with genetic or physiologic conditions that make them more likely to develop blood clots in their veins (venous thrombosis). Scientists have recently learned that these congenital problems, which include genetic mutations that affect proteins in blood that regulate clotting, are more common and more varied than had been thought. Researchers have also recently discovered that certain disorders are likely to affect younger people, while other conditions can cause clots at any age. They have also learned that some, but not all, coagulation problems may predispose patients to recurrent blood clots. Since much of the knowledge is new, the authors propose that classifying congenital blood-clotting problems into two major groups may help clinicians diagnose and treat their patients who develop venous thrombosis.

Many of the conditions that predispose people to developing blood clots were discovered by scientists in the 1980s and 1990s. The authors suggest that because of rapid advances in the field, clinicians can better help their patients if they have a practical, evidence-based method for thinking about possible clotting problems.

Using MEDLINE, a National Library of Medicine service that enables computerized searches of the medical literature, the authors identified all articles published in English from 1998 to May 2001 that addressed inherited blood clotting conditions in humans.

Given the state of the knowledge about congenital problems that may cause patients to develop blood clots, the authors propose that these disorders be categorized into two general groups. The first group includes conditions that occur when a person has too little of what keeps blood from clotting too much (for example, antithrombin deficiencies). These are less common, but potentially more dangerous. About 60% of patients with these deficiencies will develop a blood clot by age 60 years. Patients with the second set of conditions have too much of the substances that cause blood to clot (prothrombin and other clotting factors). These disorders are more common in the population; however, patients with these disorders can develop blood clots at any age, and these disorders may not be risk factors for recurrent blood clotting problems. The authors also list several conditions that fall outside this classification system and point out that many patients with blood clots may have more than one risk factor for developing them.

Grouping congenital causes of venous thrombosis may help clinicians and patients think about their risk for developing blood clots. This, in turn, may lead them to consider whether certain treatments—such as medicine used to prevent blood clots forming—are right for them.