829
edits
Changes
no edit summary
==Description==
==Description==
Platelets (or thrombocytes) are responsible for primary haemostasis, the formation of a temporary platelet plug that initially seals any breach to a blood vessel wall. Bleeding disorders may occur if platelets are deficient ('''thrombocytopaenia''') or if the platelets are unable to function adequately ('''thrombocytopathia'''). Thrombocytopaenia may be a '''primary disease''' due to disease of the bone marrow that reduces the production of platelets or it may occur '''secondary''' to another insult.
Platelets (or thrombocytes) are responsible for primary haemostasis, the formation of a temporary platelet plug that initially seals any breach to a blood vessel wall. Bleeding disorders may occur if platelets are deficient ('''thrombocytopaenia''') or if the platelets are unable to function adequately ('''thrombocytopathia'''). Thrombocytopaenia may be a '''primary disease''' due to disease of the bone marrow that reduces the production of platelets or it may occur '''secondary''' to another insult. '''Thrombocytosis''' refers to an increase in the blood platelet concentration above the normal level.
==Thrombocytopaenia==
===Primary Thrombocytopaenic Disease===
===Primary Thrombocytopaenic Disease===
The aetiology of primary thrombocytopenic disease is often uncertain and it is therefore also known as '''idiopathic''' thrombocytopaenia. Some cases of primary thrombocytopaenia may occur due to autoimmune responses directed at platelets and, although the [[Bone Marrow - Anatomy & Physiology|bone marrow]] may contain adequate normal megakaryocytes, this disease results in a reduced peripheral blood thrombocyte count. [[Immune Mediated Thrombocytopaenia|Immune-mediated thrombocytopaenia]] occurs most commonly in young animals.
The aetiology of primary thrombocytopenic disease is often uncertain and it is therefore also known as '''idiopathic''' thrombocytopaenia. Some cases of primary thrombocytopaenia may occur due to autoimmune responses directed at platelets and, although the [[Bone Marrow - Anatomy & Physiology|bone marrow]] may contain adequate normal megakaryocytes, this disease results in a reduced peripheral blood thrombocyte count. [[Immune Mediated Thrombocytopaenia|Immune-mediated thrombocytopaenia]] occurs most commonly in young animals.
*Diseases that cause '''[[Bone Marrow - Anatomy & Physiology|bone marrow]] suppression'''
*Diseases that cause '''[[Bone Marrow - Anatomy & Physiology|bone marrow]] suppression'''
**'''Aplastic anaemia''' caused by ingestion of bracken, administration of oestrogens or of [[Chloramphenicol|chloramphenicol]] or [[Sulphonamides|sulphonamide]] antibiotics. Prolonged use of phenylbutazone or salicylate may cause the same disease.
**'''Aplastic anaemia''' caused by ingestion of bracken, administration of oestrogens or of [[Chloramphenicol|chloramphenicol]] or [[Sulphonamides|sulphonamide]] antibiotics. Prolonged use of phenylbutazone or salicylate may cause the same disease.
**'''Myelophthisis''', the displacement of the normal tissues of the bone marrow by another cell or tissue type may also reduce the function of the megakaryocytes. Possible diseases include '''myelofibrosis''' and '''immunoprliferative''' or '''myeloproliferative''' neoplastic disease.
**'''Infectious diseases''' that reduce stem cell function, including [[Distemper|canine distemper virus]], [[Canine Parvovirus|canine parvovirus]] and [[Feline Panleucopaenia|feline panleucopaenia virus]].
**'''Myelophthisis''', the displacement of the normal tissues of the bone marrow by another cell or tissue type may also reduce the function of the megakaryocytes. Possible diseases include '''myelofibrosis''' and '''immunoproliferative''' or '''myeloproliferative''' neoplastic disease.
**'''Radiotherapy''' or myelosuppressive '''chemotherapy''' may cause reversible bone marrow suppression.
**'''Radiotherapy''' or myelosuppressive '''chemotherapy''' may cause reversible bone marrow suppression.
*Diseases that cause '''increased destruction of platelets'''
*Diseases that cause '''increased destruction of platelets'''
**'''Infectious diseases''' that cause destruction of platelets, including [[Bovine Viral Diarrhoea Virus|bovine viral diarrhoea]], [[Classical Swine Fever|classical swine fever]] and [[Infectious Canine Hepatitis|infectious canine hepatitis]]. The parasites ''[[Ehrlichia platys]]'', ''[[Anaplasma phagocytophilum]]'' and ''[[Ehrlichia canis]]'' may also cause infectious thrombocytopaenia. Any severe bacterial infection, including those caused by [[:Category:Staphylococcus species|''Staphylococci'']] and the Gram negative bacteria that produce endotoxin (e.g. [[:Category:Pseudomonas and Burkholderia species|''Pseudomonas spp.'']] or [[Salmonella|''Salmonella spp.'']]) may also result in the destruction of platelets.
*Diseases that cause '''sequestration of platelets''' usually involve some enlargement to the spleen as this is the major organ where platelets are stored outside of the circulation. Examples include:
*Diseases that cause '''sequestration of platelets''' usually involve some enlargement to the spleen as this is the major organ where platelets are stored outside of the circulation. Examples include:
**[[Haemangiosarcoma]] of the spleen and liver
**[[Haemangiosarcoma]] of the spleen and liver
**Splenic enlargement under general anaesthesia with certain agents such as barbiturates and phenothiazines
**Splenic enlargement under general anaesthesia maintained with agents such as [[Barbiturates|barbiturates]] and [[Phenothiazines|phenothiazines]]
*'''Artefactual''' or spurious thrombocytopaenia
**'''Cavalier King Charles spaniels''' have a relatively small number of giant platelets (macrothrombocytes) but they do not suffer from bleeding disorders as they maintain a similar total platelet mass as do dogs of other breeds.
**If venepuncture is traumatic, '''platelet clumps''' may form and these will not be counted by automated machines. The presence of clumps can be investigated by making a blood smear and examining the feathered edge for large agglomerations of platelets.
==Thrombocytopathia==
{{unfinished}}
{{unfinished}}
Von Willebrands, Angiostrongylus, colloids, granule disease.
Von Willebrands, Angiostrongylus, colloids, Pelger Huet anomaly?.
* A rare inherited condition.
* A rare inherited condition.
* Recorded in the dog.
* Recorded in the dog.
** Poor aggregations.
** Poor aggregations.
** Poor platelet factor release.
** Poor platelet factor release.
==Thrombocytosis==
Increases in platelets above the normal level may occur due to '''physiological''' or '''pathological''' processes.
*Physiological
**'''Splenic contraction''' pushes sequestered platelets into the circulation. This phenomenon is especially marked in horses which have a muscular splenic capsule.
**As part of a response to '''anaemia''', a rebound thrombocytosis is often documented and this may precede signs of regeneration.
*Pathological
**'''Essential thrombocythaemia'''
**Megakaryocytic leukaemia
[[Category:Haemorrhagic Diseases]]
[[Category:Haemorrhagic Diseases]]
[[Category:To Do - James]]
[[Category:To Do - James]]