Failures of primary haemostasis

Question 1

What are the 3 main types of abnormality that can lead to failure of primary haemostasis?

Answer 1

Vascular
Platelet
Von Willebrand Factor

Question 2

What are the 2 main types of platelet abnormality?

Answer 2

• Reduced platelet count (Thrombocytopenia)
• Reduced platelet function

Question 3

What are some heredity causes of vascular abnormality?

Answer 3

• Marfan’s
• Ehlers Danlos
• Luiz Dietz

Question 4

What are some acquired causes of vascular abnormality?

Answer 4

• Vasculitis
• Scurvy
• Ageing
• Long term steroid use

Question 5

What is thrombocytopenia?

Answer 5

Thrombocytopenia is a reduced platelet count and is the most common cause of primary haemostatic failure

Question 6

What are the main 2 mechanisms of acquired thrombocytopenia?

Answer 6

Reduced production
Increased destruction

Question 7

What is the most common cause of reduced platelet production?

Answer 7

Bone marrow failure, usually caused by malignancy

Question 8

What are some possible causes of peripheral platelet destruction?

Answer 8

• Coagulopathy (E.g. Disseminated intravascular coagulation)
• Autoimmune (E.g. Immune thrombocytopenia purpura)
• Hypersplenism

Question 9

What is the most common cause of hypersplenism?

Answer 9

Liver disease and cirrhosis

Question 10

What are the most common causes of acquired platelet dysfunction?

Answer 10

• Drugs (e.g. aspirin, NSAIDs)
• Renal failure

Question 11

What is Von Willebrand factor deficiency?

Answer 11

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

Question 12

Describe the pathophysiology of VWF deficiency

Answer 12

• 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)

Question 13

How is von Willebrand factor deficiency diagnosed?

Answer 13

• FBC
• Coagulation tests
• vWF antigen testing
• Factor VIII clotting activity test
• Specialised vWF testing (e.g. von Willebrand factor multiuser test)

Question 14

How will FBC be affected in vWF deficiency?

Answer 14

May be normal or may show microcytic anaemia or low platelet count

Question 15

How will coagulation tests be affected in vWF deficiency?

Answer 15

APTT may be normal or may be prolonged if factor VIII deficiency is present, PT will be normal

Question 16

What are some management options available in vWF deficiency?

Answer 16

• Desmopressin
• Plasma-derived factor VIII concentrates that contain intact VWF (Mainstay in bleeding treatment)
• Recombinant vWF

Question 17

What are some possible complications of failure of primary haemostasis?

Answer 17

• Spontaneous bruising
• Purpura (Fine rash)
• Mucosal bleeding
  
  • Gastrointestinal bleeding
  • Conjunctival bleeding
  • Epistaxes (Nose bleeds)
  • Menorrhagia (Heavy menstrual bleeding)
• Intracranial haemorrhage
• Retinal haemorrhage

Question 18

What is immune thrombocytopenic purpura?

Answer 18

This is a clinical syndrome in which a decreased number of circulating platelets manifests as a bleeding tendency

Question 19

What are some causes of secondary ITP?

Answer 19

• Other autoimmune disorders
• Viral infection (e.g. CMV, Varicella-Zoster, Hep C, HIV)
• H. pylori infection
• Drugs
• Lymphoproliferative disorders

Question 20

Describe the pathophysiology of ITP

Answer 20

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

Question 21

Who usually presents with ITP?

Answer 21

Children under 10, often with a history of recent viral illness

Question 22

What are some symptoms of ITP?

Answer 22

• Bleeding (e.g. gums, epistaxis, menorrhagia)
• Ecchymosis
• Petechiae
• Purpura

Question 23

What is the main test used in ITP?

Answer 23

Full blood count showing isolated thrombocytopenia instead of a pancytopenia

Question 24

How is ITP usually managed?

Answer 24

Usually, no treatment is required and patients are monitored until platelets return to normal

Around 70% of patients will spontaneously remit within 3 months

Question 25

How are patients with ITP which who are actively bleeding or who have severe thrombocytopenia (<10) managed?

Answer 25

• Prednisolone
• IV immunoglobulins
• Blood transfusion if required
• Platelet transfusions (Temporary)