Immune thrombocytopenic purpura (ITP)

Question 1

Define immune thrombocytopenic purpura.

Answer 1

Syndrome characterised by immune destruction of platelets resulting in bruising or a bleeding tendency.

isolated thrombocytopenia in the absence of an identifiable cause

Question 2

What is the cause of ITP? Summarise the pathophysiology.

Answer 2

Idiopathic

Acute ITP: often seen after viral infection in children

Chronic ITP: more common in adults and associated with…

• infections - malaria, EBV, HIV
• AI disease - SLE, thyroid disease
• malignancies
• drugs - quinine

Autoantibodies that bind to platelet membrane proteins (Glp IIb/IIIa and Ib/IX) causes thrombocytopenia.

Question 3

Who is usually affected by ITP?

Answer 3

Acute - children between 2-7yrs

Chronic - adults, 4 times more common in women

Question 4

What are the symptoms of ITP?

Answer 4

• Easy bruising e.g. petechiae and purpura
• Mucosal bleeding, menorrhagia, epistaxis
• Catastrophic bleeding e.g. intracranial

Question 5

What are the signs of ITP?

Answer 5

• Visible petechiae - primarily on lower limbs but can occur anywhere
• Bruises (purpura or ecchymoses)
• Signs of other illness e.g. infection, wasting, splenomegaly, suggests other causes.*
• Intracranial bleeding is reported in less than 1% of adults and less than 0.5% of children.

Question 6

What investigations would you do for ITP?

Answer 6

ITP is a diagnosis of exclusion: exclude myelodysplasia, acute leukaemia, marrow infiltration.

Bloods-

• FBC - low Plt
• Clotting - normal PT, APTT and fibrinogen
• Autoantibodies - antiplatelet antibody (may be present but not routinely used for diagnosis), anticardiolipin antibody (ACA), antinuclear antibody (ANA)

Blood film - rule out pseudothrombocytopaenia caused by platelet clumping giving falsely low counts

Bone marrow - exclude other pathology. May show normal or raised megakaryocytes.

Others to exclude:

• HIV serology
• H pylori breath test (although this rarely causes very low platelet counts)
• Hep C serology
• TFTs
• Bone marrow aspiration
• Pregnancy test (some treatments for ITP cannot be given to pregnant women)

Question 7

What is the platelet count in thrombocytopenia?

Answer 7

<100× 10⁹/L

Question 8

What are antibodies in ITP directed against?

Answer 8

glycoproteins:

• IIb/IIIa
• Ib-V-IX complex.

Question 9

What is the management of ITP?

Answer 9

Oral prednisolone (first line)

Pooled IVIG - raises plt faster than steroids so used in active bleeding

Splenectomy (less common)

Question 10

What is Evan’s syndrome?

Answer 10

ITP in association with AIHA

Question 11

What is the prognosis with ITP?

Answer 11

Most respond to initial steroids

More than half need additional course of steroids

Prognosis generally good - children often recover spontaneously