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Haematology > Thrombocytopenia > Flashcards

Thrombocytopenia Flashcards

1
Q

What is the normal platelet range?

A

150-450 x10^9

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2
Q

What are the two categories which cause low platelets?

A

Decreased production
Increased destruction

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3
Q

What can cause reduced platelet production?

A
  • Viral infections e.g. EBV, CMV, HIV
  • B12 deficiency
  • Folate deficiency
  • Liver failure - reduced thrombopoietin production
  • Leukaemia
  • Myelodysplastic syndrome
  • Chemotherapy
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4
Q

What can cause increased platelet destruction?

A
  • Medications e.g sodium valproate and methotrexate
  • Alcohol
  • Immune thrombocytopenic purpura
  • Thrombotic thrombocytopenic purpura
  • Heparin-induced thrombocytopenia
  • Haemolytic uraemic syndrome
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5
Q

How can thrombocytopenia present?

A

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

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6
Q

What are the most likely differentials for abnormal bleeding?

A

Thrombocytopenia
Von Willebrand disease
Haemophilia A and B
Factor V Leiden (abnormal factor V so protein C doesn’t bind- hypercoaguability)

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7
Q

What is immune thrombocytopenic purpura?

A

Antibodies created against platelets leading to destruction and low platelet count

Characteristically presents with purpura

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8
Q

How is immune thrombocytopenic purpura managed?

A

Monitoring platelet count, controlling BP and suppressing menstrual periods

  • Prednisolone
  • IV immunoglobulins
  • Thrombopoietin receptor agonists
  • Rituximab
  • Splenectomy
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9
Q

What is an example of a thrombopoietin receptor agonist?

A

Avatrombopag

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10
Q

How does Rituximab work?

A

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

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11
Q

What is thrombotic thrombocytopenic purpura?

A

Condition where tiny thrombi develop throughout small vessels using up platelets

Microangiopathy as it effects small vessels

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12
Q

What does thrombotic thrombocytopenic purpura cause?

A

Thrombocytopenia
Purpura
Tissue ischaemia and end-organ damage

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13
Q

Why do thrombi develop in thrombotic thrombocytopenic purpura?

A

Issue with ADAMTS13 protein

Results in accumulation of high molecular weight VWF which is highly active

ADAMTS13 usualyl cleaves high molecular weight VWF

Leads to excess platelet activation and clumping causing microangiopathic haemolytic anaemia

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14
Q

Why is there a normal PT, APTT, fibrinogen and d-dimer in thrombotic thrombocytopenic purpura?

A

Clotting cascade not activated

Clotting factors not consumed results in normal coagulation screen

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15
Q

How does thrombotic thrombocytopenic purpura present?

A

Pentad of symptoms
AKI
Neurological features
Microangiopathic haemolytic anaemia
Low platelets
Fever

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16
Q

What can cause a deficiency in ADAMTS13 protein?

A

Inherited
Autoimmune disease, antibodies attack the protein

17
Q

How is thrombotic thrombocytopenic purpura treated?

A

Plasma exchange(removes circulating antibodies)
Steroids
Rituximab

18
Q

What happens in Heparin-Induced Thrombocytopenia?

A

Development of antibodies against platelets in response to heparin

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

19
Q

What type of heparin usually causes heparin-induced thrombocytopenia?

A

Unfractionated

Can also occur with low-molecular-weight heparin

20
Q

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

A

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

21
Q

How is Heparin-induced thrombocytopenia diagnosed?

A

Blood sample

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

Haematology (18 decks)

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