Category:Haemorrhagic Diseases

• There is a wide range of diseases and syndromes that are characterised by haemorrhagic disease.
• Show either:
  • An increased tendency to bleeding - haemorrhagic diathesis.
  • Frank haemorrhages as a clinical feature - purpura.
• Altought this disease is sometimes obvious, it may also be discovered incidentally, for examply following surgery or trauma.

Classification of Haemorrhagic Diseases

• Haemorrhagic diseases may be due to
  1. Increased vessel fragility.
     • Causes non-thrombocytopenic purpura.
  2. Inadequate haemostatic response.
     • This may be caused by:
       • Platelet dysfunction or deficiency.
         • Causes primary or secondary thrombocytopenic purpura.
       • Deficiencies or derangements of clotting factors.
• Syndromes caused by vascular fragility and platelet dysfunction tend to be purpuric and aquired.
• Sydromes caused by clotting factor defects tend to cause more severe bleeding and are usually congenital.

Vascular Fragility

Disease associated with platelet abnormalities

Primary Thrombocytopenic Disease

• The aetiology of primary thrombocytopenic disease is often uncertain.
  • It is therefore also known as idiopathic thrombocytopenia.
  • The cause may be automimmune.
• Although the bone marrow contains adequate normal megakaryocytes, there is a reduced peripheral blood thrombocyte count.
• Usually seen in young animals.

Secondary Thrombocytopenic Disease

• Secondary thrombocyopaenic disease is fairly common in adult and older domestic animals.
• Associated with diseases which cause bone marrow depression.
• The bone marrow is depleted or devoid of megakaryocytes, and there is a nil or markedly reduced peripheral blood thrombocyte count.
• Secondary thrombocyopenic disease is seen in the following conditions:
  1. Severe viral infections.
     • For examople, ICH, feline panleucopenia, mucosal disease, swine fever.
  2. Severe protozoal infections.
     • For example, in the UK, Haemobartonella may be a cause.
  3. Plant intoxications.
     • For example, bracken, kale, or ragwort poisoning.
  4. Drug-induced conditions.
     • High doses of oestrogens and salicylate.
     • Prolonged use of phenyl butazone.
  5. bone marrow neoplasia.
     • For example, lymphosarcoma or myeloid leukaemia.
  6. Radiation.
     • May cause damage to the bone marrow if it is severe and generalised.
  7. Other miscellaneous causes.
     • Severe bacterial infections.
       • For example, Staphylococci, and those Gram -ve bacteria producing endotoxins (e.g. Pseudomonas or Salmonella spp.).
     • Liver disease.

Thrombocytopathia

• A rare inherited condition.
• Recorded in the dog.
• Characterised by defective thrombocyte formation.
  • Poor adhesiveness.
  • Poor aggregations.
  • Poor platelet factor release.

Diseases associated with coagulation factor defects

• Most cases of "factor disease" in animals are similar to those studied in man.
  • Congenital.
  • Based on familial occurence.
  • Clotting biochemistry is similar in man and animals.
• Most investigations have been carried out in the dog.
• Haemophilia (factor VIII deficiency) is probably the best understood condition.

Von Willebrand's Disease

• Seen in the dog.
  • Most common in Scottish Terriers and Chesapeake Bay Retrievers.
  • Has been seen more 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.
• Presentation
  • Purpura.
  • Prolonged bleeding time.
  • Reduced platelet adhesiveness.
  • Low Factor XIII levels.
• The disease can be assessed by the measurement of Von Willebrand Factor protein levels.
  • A Factor VIII-related protein.
  • Synthesised in endothelial cells and megakaryocytes.
  • Stored in platelets.
  • Levels are low in affected animals.

Deficiency states of other factors have been recorded sporadically as follows:

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.