THE INVESTIGATION OF A PATIENT WITH UNEXPECTED VENOUS THROMBOSIS

Over recent years a number of hereditary and acquired defects of the c irculation's natural anticoagulant mechanisms have been characterised and shown to predispose affected individuals to thrombosis. It is impo rtant to attempt to diagnose a thrombophilia state in patients with a thrombotic tendency in order to provide appropriate management, especi ally during at-risk situations, both for themselves and asymptomatic r elatives identified through family studies. This review defines the pa tients who should be investigated for an underlying thrombophilia stat e and describes the hereditary and acquired disorders which should be screened for within an investigation profile. The recently identified factor V Leiden mutation which appears to be the most common hereditar y cause of a thrombotic tendency is described in detail and descriptio ns of the more established thrombophilia states are included. Although the factor V Leiden mutation accounts for a significant proportion of cases fulfilling the criteria for thrombophilia screening, a predispo sing cause for thrombosis remains unidentifiable in a large number of patients making it likely that over the years to come new thrombophili a states will continue to be identified.