immune thrombocytopenic purpura

Question 1

definition of immune thrombocytopenic purpura

Answer 1

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

Question 2

aetiology of immune thrombocytopenic purpura

Answer 2

often idiopathic

acute - 2wk after viral infection in children

chronic form more common in adults

possible associations

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

Autoantibodies that bind to platelet membrane proteins (glycoprotein IIb/IIIa and Ib/IX) results in thrombocytopaenia.

Question 3

epidemiology of immune thrombocytopenic purpura

Answer 3

acute: 2-7yrs
chronic: adults,

4x more common in women

Question 4

sx of immune thrombocytopenic purpura

Answer 4

easy bruising

mucosal bleeding

menorrhagia

epistaxis

chronic has fluctuating course of: bleeding, purpura (especially pressure dependant areas), epistaxis, and menorrhagia

Question 5

signs of immune thrombocytopenic purpura

Answer 5

visible petechiae

bruises - purpura or ecchymoses

no splenomegaly

signs of other illness (infections, wasting, splenomegaly) suggest other causes

Question 6

Ix for immune thrombocytopenic purpura

Answer 6

diagnosis of exclusion - exclude myelodysplasia, acute leukaemia, marrow infiltration

blood

blood film

bone marrow

Question 7

blood results for immune thrombocytopenic purpura

Answer 7

FBC - low platelets

clotting screen - normal PT, APTT and fibrinogne

autoAb

• antiplatelet antibody may be present but not used routinely for diagnosis,
• anticardiolipin antibody,
• antinuclear antibody)

Question 8

blood film for immune thrombocytopenic purpura

Answer 8

rule out ‘pseudothrombocytopaenia’ caused by platelet clumping giving falsely low counts.

Question 9

bone marrow findings in immune thrombocytopenic purpura

Answer 9

exclude other pathology

normal or high megakaryocytes