Haem - Thrombocytopenia

Question 1

What is the normal platelet range?

Answer 1

150-450 x10^9

Question 2

What are the two categories which cause low platelets?

Answer 2

Decreased production
Increased destruction

Question 3

What can cause reduced platelet production?

Answer 3

• Viral infections e.g. EBV, CMV, HIV
• B12 deficiency
• Folate deficiency
• Liver failure - reduced thrombopoietin production
• Leukaemia
• Myelodysplastic syndrome
• Chemotherapy

Question 4

What can cause increased platelet destruction?

Answer 4

• Medications e.g sodium valproate and methotrexate
• Alcohol
• Immune thrombocytopenic purpura
• Thrombotic thrombocytopenic purpura
• Heparin-induced thrombocytopenia
• Haemolytic uraemic syndrome

Question 5

How can thrombocytopenia present?

Answer 5

Usually when platelets under 50x10^9

• Nosebleeds
• Bleeding gums
• Heavy periods
• Easy bruising
• Haematuria
• Rectal bleeding

Platelets below 10x10^9 are at high risk of spontaneous bleeding
- Intracranial haemorrhage
- GI bleeding

Question 6

What are the most likely differentials for abnormal bleeding?

Answer 6

Thrombocytopenia
Von Willebrand disease
Haemophilia A and B
Disseminated intravascular coagulation (usually secondary to sepsis)

Question 7

What is immune thrombocytopenic purpura?

Answer 7

Antibodies created against platelets leading to destruction and low platelet count

Characteristically presents with purpura

Question 8

How is immune thrombocytopenic purpura managed?

Answer 8

Monitoring platelet count, controlling BP and suppressing menstrual periods

• Prednisolone
• IV immunoglobulins
• Thrombopoietin receptor agonists
• Rituximab
• Splenectomy

Question 9

What is an example of a thrombopoietin receptor agonist?

Answer 9

Avatrombopag

Question 10

How does Rituximab work?

Answer 10

Targets CD20 proteins on surface of B cells

By attacking B cells and reducing their number, it reduces production of antibodies that are causing autoimmune disease

Question 11

What is thrombotic thrombocytopenic purpura?

Answer 11

Condition where tiny thrombi develop throughout small vessels using up platelets

Microangiopathy as it effects small vessels

Question 12

What does thrombotic thrombocytopenic purpura cause?

Answer 12

Thrombocytopenia
Purpura
Tissue ischaemia and end-organ damage

Question 13

Why do thrombi develop in thrombotic thrombocytopenic purpura?

Answer 13

Issue with ADAMTS13 protein
Normally the protein :
- Inactivates Von Willebrand factor
- Reduced platelet adhesion to vessel walls
- Reduces clot formation

Question 14

What can cause a deficiency in ADAMTS13 protein?

Answer 14

Inherited
Autoimmune disease, antibodies attack the protein

Question 15

How is thrombotic thrombocytopenic purpura treated?

Answer 15

Haematologist guided

Plasma exchange
Steroids
Rituximab

Question 16

What happens in Heparin-Induced Thrombocytopenia?

Answer 16

Development of antibodies against platelets in response to heparin

Heparin-induced antibodies target Platelet factor 4 on platelets (PF4)

Question 17

What type of heparin usually causes heparin-induced thrombocytopenia?

Answer 17

Unfractionated

Can also occur with low-molecular-weight heparin

Question 18

How long does heparin-induced thrombocytopenia take to present after heparin initiation?

Answer 18

5-10 days

HIT antibodies bind to platelets and activate clotting system causing hypercoagulable state and thrombosis

Also break down platelets causing thrombocytopenia

Patient can therefore have low platelet count and develop abnormal blood clots

Question 19

How is Heparin-induced thrombocytopenia diagnosed?

Answer 19

Blood sample

Stop heparin and use another anticoagulant e.g. fondaparinux or argatroban