Clotting disorders

Genetic defects characterized by (a) lack of expression or (b) an altered amino acid sequence of any clotting factor can have serious clinical consequences. In order to promote effective clotting, both intrinsic and extrinsic coagulation pathways must be functional, and the inhibition of even one of these pathways will result in severely retarded coagulation ability. The result is usually occurrence of spontaneous bruising and prolonged haemorrhage, which can be fatal. With the exception of tissue factor and Ca2+, defects in all other clotting factors have been characterized. Up to 90 per cent of these, however, relate to a deficiency in factor VIII, and much of the remainder is due to a deficiency in factor IX.

Table 12.2 Recombinant blood coagulation factors that have been approved for the management of coagulation disorders

Product (tradename)

Company

Indication

Advate (rhFactor VIII) Bioclate (rhFactor VIII) Benefix (rhFactor IX) Kogenate (rhFactor VIII) Helixate NexGen (rhFactor VIII) NovoSeven (rhFactor VIIa) Recombinate (rhFactor VIII) ReFacto (B-domain deleted rhFactor VIII)

Baxter Aventis

Genetics Institute

Bayer

Bayer

Novo-Nordisk

Baxter Healthcare/Genetics Institute Genetics Institute

Haemophilia A Haemophilia A Haemophilia B Haemophilia A Haemophilia A Some forms of haemophilia Haemophilia A Haemophilia A

Such clotting disorders are generally treated by ongoing administration of whole blood or, more usually, concentrates of the relevant coagulation factor purified from whole blood. This entails significant risk of accidental transmission of blood-borne disease, particularly hepatitis and AIDS. In turn, this has hastened the development of blood coagulation factors produced by genetic engineering, several of which are now approved for general medical use (Table 12.2).

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