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About thrombosis
Thrombophilia: acquired thrombophilia
Myeloproliferative disorders
Myeloproliferative disorders (MPD) include blood disorders such as polycythaemia vera, idiopathic myelofibrosis, chronic myelogenous leukaemia and essential or primary thrombocythaemia (ET). Both polycythaemia vera and essential thrombocythaemia can lead to thrombosis.
Polycythaemia vera
Polycythaemia vera is due to a sustained elevation
in the blood's red cell count. There may also be an elevated platelet count
and white cell count. Individuals with this condition have an increased risk
of both venous thrombosis and arterial
thrombosis, unless excess numbers of cells are reduced by the use of venesection,
when up to a half a litre of blood is taken away, or with certain cytotoxic
drugs. These drugs control the disease by reducing the number of cells made
in the bone marrow.
Essential or primary thrombocythaemia
Essential or primary thrombocythaemia (ET) results from a sustained elevation
in the blood platelet count. Arterial
or venous thrombosis is one of the most
common complications of ET. Thrombosis may occur anywhere in the body, but
the majority tend to affect large arteries. Individuals with ET are therefore
at particular risk of strokes and heart attacks. Small blood vessels may
also be affected.
People with this condition may have headaches and thrombosis in the fingers. This is often associated with painful, red toes or fingers, known as erythromelalgia. Venous thrombosis is less common in people with ET. However thromboses may occur in unusual places, such as the abdomen.
Between 50 and 80 per cent of individuals with ET show symptoms of thrombosis. While symptoms appear to be more common in those with high blood platelet counts, there is no clear correlation between the degree of thrombocythaemia and the risk of thrombosis.
Treatment of ET
Treatment of ET aims to reduce the risk of thrombosis by giving aspirin
and other antiplatelet drugs, such as clopidogrel, and by reducing
the platelet count with certain cytotoxic drugs, such as hydroxyurea.
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