Bleeding disorders

A group of conditions characterized by bleeding in the absence of injury or by abnormally prolonged and excessive bleeding after injury. The disorders result from defects in mechanisms by which bleeding is normally stopped: blood coagulation, plugging of damaged blood vessels by platelets, and constriction of blood vessels (see blood clotting). Coagulation disorders are usually due a deficiency of or abnormality in the enzymes (coagulation factors) involved in blood clotting. Defects may be congenital or acquired later in life. The main congenital coagulation defects are von Willebrand’s disease, haemophilia, and Christmas disease. Acquired defects of coagulation factors may develop at any age due to severe liver disease, digestive system disorders that prevent the absorption of vitamin K (needed to make certain coagulation factors), or the use of anticoagulant drugs. Disseminated intravascular coagulation (DIC) is an acquired disorder that is both complex and serious. It may be the result of underlying infection or cancer. In this condition, platelets accumulate and clots form within small blood vessels; coagulation factors are used up faster than they can be replaced, and severe bleeding may result. Coagulation disorders are treated by replacement of the missing factor, factors extracted from fresh blood, or fresh frozen plasma. Genetically engineered factors may be used. Anticoagulants are sometimes used to suppress excess clotting activity in DIC. Thrombocytopenia, which results from insufficient platelets in the blood, produces surface bleeding into the skin and gums and multiple small bruises. Platelet defects may be inherited, associated with the use of certain drugs (including aspirin), or a complication of certain bone marrow disorders such as myeloid leukaemia. Treatment consists of platelet transfusions. Rarely, abnormal bleeding is caused by a bloodvessel defect or scurvy. Elderly people and patients on long-term courses of corticosteroid drugs may suffer mild abnormal bruising due to loss of skin support to the smallest blood vessels. Treatment is rarely required.


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