Thrombocytopaenia

Question 1

Thrombocytopaenia

What is it?

Causes can be split into?

Answer 1

Thrombocytopenia describes a low platelet count. The normal platelet count is between 150 to 450 x 109/L.

They can be split into problems with production or destruction.

Question 2

Causes of reduced production of platelets

Answer 2

Sepsis

B12 or folic acid deficiency

Liver failure causing reduced thrombopoietin production in the liver

Leukaemia

Myelodysplastic syndrome

Question 3

Causes of increased pathological of platlets

Answer 3

Medications (sodium valproate, methotrexate, isotretinoin, antihistamines, proton pump inhibitors)

Alcohol

Immune thrombocytopenic purpura

Thrombotic thrombocytopenic purpura

Heparin induced thrombocytopenia

Haemolytic-uraemic syndrome

Question 4

Clinical Features

Answer 4

Platelet counts below 50 x 109/L:

• easy or spontaneous bruising
• prolonged bleeding times
• nosebleeds
• bleeding gums
• heavy periods
• blood in the urine or stools.

Platelet counts below 10 x 109/L are high risk for spontaneous bleeding. Spontaneous intracranial haemorrhage or GI bleeds are particularly concerning.

Question 5

Differentials

Answer 5

Von Willebrand disease

Haemophilia A+B

Dissesminated intravascular coagulation (secondary to sepsis)

Question 6

Immune Thrombocytopenia Purpura (ITP)

Answer 6

Antibodies directed against the glycoprotein IIb/IIIa or Ib-V-IX complex

So antibodies that destroy platelets

Question 7

ITP Management

Answer 7

Prednisolone (steroids)
IV immunoglobulins
Rituximab (a monoclonal antibody against B cells)
Splenectomy

Safety netting

Question 8

Thrombotic Thrombocytopenia Purpura

Answer 8

tiny blood clots develop throughout the small vessels of the body using up platelets and causing thrombocytopenia

Clinical features:

• bleeding under the skin
• other systemic issues due to microangiopathy

Question 9

Thrombotic Thrombocytopenia Purpura Pathology

Answer 9

ADAMTS13 mutation

This protein normally inactivates von Willebrand factor so a shortage in this protein leads to von Willebrand factor overactivity and the formation of blood clots in small vessels.

This causes platelets to be used up leading to thrombocytopenia.

The blood clots in the small vessels break up red blood cells, leading to haemolytic anaemia.

Question 10

Management

Answer 10

plasma exchange

steroids

rituximab

Question 11

Heparin Induced Thrombocytopaenia

Pathology

Management

Answer 11

Heparin induced thrombocytopenia (HIT) involves the development of antibodies against platelets in response to exposure to heparin (anti-PF4/heparin antibodies)

The HIT antibodies bind to platelets and activate clotting mechanisms.

This causes a hypercoagulable state and leads to thrombosis.

They also break down platelets and cause thrombocytopenia.

Therefore there is an unintuitive situation where a patient on heparin with low platelets forms unexpected blood clots.

Management is by stopping heparin and using an alternative anticoagulant guided by a specialist.