(1) Factor VIII preparations in the treatment of haemophilia and von Willebrand's syndrome. It should be appreciated that despite the recognition of many genetically determined coagulation defects, haemophilia is the only relatively common hereditary coagulation defect. The incidence is of the order of 1 per 20 000 of the population. Although relatively rare, the severe haemophiliac has so many problems that relevant therapeutic issues impinge more frequently on the physician than the incidence rate would indicate. These preparations also have a role in the rarer disorder of von Willebrand's syndrome, which is a genetically determined haemorrhagic state characterised by a prolonged bleeding time and often by a deficiency of factor VIII.

Plasma is used in the treatment of these conditions either as whole plasma or as one of its fractions —a simple prepared fraction called cryoprecipitate or as a lyophil dried preparation made by much more sophisticated and expensive techniques.

(2) Consideration must also be given to factor IX in the treatment of haemophilia B or Christmas disease.

In some ways this is easier to treat while in others it is more difficult. It is easier in the sense that factor IX is much less labile than factor VIII, but cryoprecipitate does not contain therapeutic amounts of factor IX and there is no equivalent simple fractionation procedure for factor IX. The ‘purified’ fractions are prepared by relatively more sophisticated and expensive techniques.

(3) In the management of vitamin K deficiency, oral anticoagulant therapy or liver disease then purified preparations of factors II, VII, IX and X may be required.

(4) In the defibrination syndrome fibrinogen may be needed.