Coagulation Factor Deficiency

Introduction

Factor deficiencies are often the result of congenital deficiency in one or more of the coagulation factors. Deficiencies lead to ineffective blood clotting and development of a disease syndrome characterized by excessive bleeding - deficiencies are often detected following trauma or surgery. Occasionally bleeding may be spontaneous (e.g. into alimentary or urinary tracts). Deficiencies are often seen as familial inherited problems. Haemophilia (factor VIII deficiency) is probably the best understood condition.

Von Willebrand's Disease

This condition is seen in the dog, most frequently in Scottish Terriers and Chesapeake Bay Retrievers. It has become more prevalent recently in Dobermanns, Setters and German Shepherd dogs. A similar disease has been recorded in the pig.

Von Willebrand's Disease is an inherited autosomal recessive trait. It is incompletely dominant, so there is variable expression. It can present as purpura and/or prolonged bleeding times. Pathologically, there is reduced platelet adhesiveness and low Factor XIII levels.

The disease can be assessed by the measurement of Von Willebrand Factor protein levels; levels are low in affected animals. The Von Willebrand Factor protein bind to Factor VIII, and is synthesised in endothelial cells and megakaryocytes and stored in platelets.

Factor I

Factor 1 is fibrinogen. Hyperfibrinogenaemia occurs in

• Pregnancy
• Acute infections
• Post-operative states
• Pyometra

Hypofibrinogenaemia is seen in

• Liver disease.
• Depletion by intravascular coagulation.

Factor II

• Factor II is part of the prothrombin complex.
• Hypoprothrombinaemia
  • A depression of the components of the prothrombin complex.
    • I.e. Factors II, VII, IX, X
  • May be caused by dicoumarol and its derivatives, for example sweet clover and warfarin.
    • Competitively inhibits Vitamin K in the liver, where the above Factors are synthesised.

Factor IV

• Factor IV is calcium.
  • Necessary at several stages of coagulation.
• Hypocalcaemia at a level sufficient to impair haemostasis is incompatible with life.
  • There is therefore no bleeding defect associated with hypocalcaemia.

Factor VII

• Factor VII is Proconvertin.
• Deficiencies do not appear to impair the formation of haemostatic plug.
  • The bleeding defect is normally mild.
• Newborn pups have a very low plasma level of Factor VII.
  • Spontaneous and inherited deficiencies have been reported in Beagle colonies.
• Deficiencies may also occur associated with liver disease and in dicoumarol poisoning.

Factor VIII

• Factor VIII is known as antihaemophilic factor (AHF).
• Deficiency of this factor causes haemophilia A.
  • The primary thrombocyte plug is abnormal.
    • More vascular channels than usual.
    • Less fibrin-collagen contact around the edges.
  • Plugs are therefore easily dislodged.
    • Results in rebleeding.
    • Secondary plugs only form with difficulty.
• Haemophilia is reported in horses and in around 20 breeds of dogs.
• Haemophilia is as a sex-linked recessive condition.
  • Associated with the X chromosome.
  • Affects males only.
• The severity of the disease correlates with the Factor VIII levels.
• Haematomas and haemarthrosis are common lesions.

Factor IX

• Factor IX is Christmas Factor.
• Deficiency causes haemophilia B.
  • Seen in Cairn Terriers and Black and Tan Hounds.
  • A sex-linked (X chromosome) recessive.
  • Results in a deficient haemostatic plug.
    • Similar to Factor VIII deficiency.

Factor XI

• Factore XI is Plasma Thromboplastin Antecedent.
• Deficiency has been reported in a cow, and reduced levels in the horse.

Factor XII

• Factor XII is Hageman Factor.
• Low plasma levels had been reported in cats and horses.