The main clinical sign associated with congenital thrombophilia is DVT. In some cases, particularly in the presence of major hyperhomocysteinaemia associated with cystathionine beta-synthase deficiency, arterial thrombosis may occur, in particular in the form of myocardial infarction in young subjects.
Clinical expression varies widely from one patient to another despite similar risk factors. Venous thromboembolic disease is multifactorial and the association of one or more congenital risk factors with environmental factors accounts for the heterogeneous nature of clinical presentations.
The clinical signs of DVT are relatively non-specific: in the absence of assay of D-dimers (specific fibrin degradation products) and imaging (Doppler ultrasound) to rule out DVT, diagnosis may be complex in certain patients.
Clinical presentations of a single abnormality can vary widely from one subject to another. In some patients, the abnormality may be diagnosed through laboratory tests in the absence of any clinical signs, a situation referred to as biological thrombophilia.