Failures of primary haemostasis Flashcards
What are the 3 main types of abnormality that can lead to failure of primary haemostasis?
Vascular
Platelet
Von Willebrand Factor
What are the 2 main types of platelet abnormality?
- Reduced platelet count (Thrombocytopenia)
- Reduced platelet function
What are some heredity causes of vascular abnormality?
- Marfan’s
- Ehlers Danlos
- Luiz Dietz
What are some acquired causes of vascular abnormality?
- Vasculitis
- Scurvy
- Ageing
- Long term steroid use
What is thrombocytopenia?
Thrombocytopenia is a reduced platelet count and is the most common cause of primary haemostatic failure
What are the main 2 mechanisms of acquired thrombocytopenia?
Reduced production
Increased destruction
What is the most common cause of reduced platelet production?
Bone marrow failure, usually caused by malignancy
What are some possible causes of peripheral platelet destruction?
- Coagulopathy (E.g. Disseminated intravascular coagulation)
- Autoimmune (E.g. Immune thrombocytopenia purpura)
- Hypersplenism
What is the most common cause of hypersplenism?
Liver disease and cirrhosis
What are the most common causes of acquired platelet dysfunction?
- Drugs (e.g. aspirin, NSAIDs)
- Renal failure
What is Von Willebrand factor deficiency?
This is a hereditary condition caused by an autosomal dominant mutation, resulting in a lack of production of von Willebrand factor
This is a common (1%) condition with variable severity, though it is mostly mild
Describe the pathophysiology of VWF deficiency
- Mutations in vWF gene on chromosome 12
- Absence of vWF leads to impaired platelet adhesion to the sub-endothelium
- Reduced vWF levels also lead to factor VIII deficiency, as factor VIII is not protected from premature degradation (vWF is responsible for transport of factor 8 in the body)
How is von Willebrand factor deficiency diagnosed?
- FBC
- Coagulation tests
- vWF antigen testing
- Factor VIII clotting activity test
- Specialised vWF testing (e.g. von Willebrand factor multiuser test)
How will FBC be affected in vWF deficiency?
May be normal or may show microcytic anaemia or low platelet count
How will coagulation tests be affected in vWF deficiency?
APTT may be normal or may be prolonged if factor VIII deficiency is present, PT will be normal
What are some management options available in vWF deficiency?
- Desmopressin
- Plasma-derived factor VIII concentrates that contain intact VWF (Mainstay in bleeding treatment)
- Recombinant vWF
What are some possible complications of failure of primary haemostasis?
- Spontaneous bruising
- Purpura (Fine rash)
- Mucosal bleeding
- Gastrointestinal bleeding
- Conjunctival bleeding
- Epistaxes (Nose bleeds)
- Menorrhagia (Heavy menstrual bleeding)
- Intracranial haemorrhage
- Retinal haemorrhage
What is immune thrombocytopenic purpura?
This is a clinical syndrome in which a decreased number of circulating platelets manifests as a bleeding tendency
What are some causes of secondary ITP?
- Other autoimmune disorders
- Viral infection (e.g. CMV, Varicella-Zoster, Hep C, HIV)
- H. pylori infection
- Drugs
- Lymphoproliferative disorders
Describe the pathophysiology of ITP
This is caused by a type II hypersensitivity reaction caused by the production of antibodies that target and destroy platelets
This can happen spontaneously, or can be triggered by something such as viral infection
Who usually presents with ITP?
Children under 10, often with a history of recent viral illness
What are some symptoms of ITP?
- Bleeding (e.g. gums, epistaxis, menorrhagia)
- Ecchymosis
- Petechiae
- Purpura
What is the main test used in ITP?
Full blood count showing isolated thrombocytopenia instead of a pancytopenia
How is ITP usually managed?
Usually, no treatment is required and patients are monitored until platelets return to normal
Around 70% of patients will spontaneously remit within 3 months
How are patients with ITP which who are actively bleeding or who have severe thrombocytopenia (<10) managed?
- Prednisolone
- IV immunoglobulins
- Blood transfusion if required
- Platelet transfusions (Temporary)
