INTRODUCTION

Abnormal thrombus formation is central to the acute pathophysiology of both arterial and venous disease. Formation of thrombus superimposed upon the surface of ruptured atherosclerotic plaque, producing vessel occlusion and resulting tissue ischemia, is the common mechanism leading to acute symptoms and presentation in patients with arterial disease. Likewise deep vein thrombosis and pulmonary embolism, important community causes of morbidity and mortality, both result from abnormal thrombus formation in the venous circulation. An understanding of conditions that may pre-dispose to abnormal thrombus formation, including a knowledge of how the presence of these conditions may or may not impact on patient management, is important for all clinicians involved in the management of vascular disease.

First used in 1937, and then also in the first description of inherited antithrombin deficiency, the term ‘thrombophilia’ can be defined as an increased tendency to develop thrombosis, which may be either acquired or inherited. Thrombophilic conditions vary both in prevalence and in the magnitude of the associated increase in risk of thrombosis. The discovery during the 1990's of the high prevalence factor V Leiden and prothrombin gene point mutations that predispose to thrombosis, meant that an underlying thrombophilic condition could be found in approximately 50% of unselected patients with venous thrombosis. This fact, along with the belief that the presence of such a condition may influence prognosis and may therefore help guide patient management, has led to a significant increase in laboratory testing for inherited thrombophilia.