Thrombophilia

Patients who are predisposed to thrombosis generally either have a disorder of the blood or an abnormality of the vessel wall. Where enhanced coagulation is the major mechanism, the disorder is referred to as ‘thrombophilia’. Patients with thrombophilia either tend to have thrombosis at an unusually early age or to develop recurrent thrombotic problems. Venous thrombosis predominates with the chance of thrombosis increased by the coexistence of other risk factors. Thrombophilia can be inherited or acquired.

Which patients should be investigated for thrombophilia?

Testing for heritable thrombophilia is not indicted in unselected patients presenting with venous thrombosis. Table 39.1 summarises factors which should prompt consideration of thrombophilia. Accurate history taking is essential; particular attention should be given to the nature of the recent thrombotic event, the presence of known risk factors (Table 39.2), a previous history of thrombosis and the family history. Definition of a ‘positive’ family history of thrombosis is problematic. If we use the simple definition of a history of deep vein thrombosis (DVT) or pulmonary embolus (PE) in a first or second degree relative, then approximately 25% of all patients will have a positive family history. Even among those with a strong family history only a small minority will have a cause of inherited thrombophilia identified.

Table 39.1

Characteristics suggesting possibility of thrombophilia

Venous thrombosis in patient less than 40 years old

Recurrent venous thrombosis or thrombophlebitis

Venous thrombosis in unusual site

Arterial thrombosis in patient less than 30 years old

Strong family history of venous thrombosis

Recurrent fetal loss

Skin necrosis in patient receiving warfarin

Purpura fulminans

Table 39.2

Major risk factors for thrombosis

Venous	Arterial
Increasing age	Increasing age
Immobility	Smoking
Obesity	Male sex
Oral contraceptive pill	Hypertension
Trauma/surgery	Strong family history
Thrombophilia (see text)	Hyperlipidaemia
Pregnancy	Diabetes mellitus
Malignancy	Raised fibrinogen