Platelet disorders Flashcards
Most frequently involved antigen in alloimmune thrombocytopenia?
anti-HPA-1a in Caucasian women
What does von Willebrand factor do in ciruclation?
Large protein which mediates the binding of platelets to the sub-endothelial space
Describe the defects in the following types of von Willebrand disease?
Type 1:
Type 2:
Type 3:
Type 1 vWD: deficiency of von Willebrands protein
Type 2 vWD: protein present, function reduced
Type 3 vWD: severe quantitative deficiency
Thrombocytopenia?
low platelet count
Thrombocytosis?
high platelet count
Which treatment modality in ITP will raise platelet count faster?
IVIG
Pathophysiology of Factor V Leiden deficiency?
Abnormal Factor V, resistant to normal anti-thrombotic effects of activated Protein C
What does Protein C do in the circulation?
Inactivates Activated factor V and factor VIII and stimulates fibrinolysis
What does anti-thrombin III do?
Inhibits thrombin and factor X
What is GPIIb/IIIa responsible for on the surface of platelets?
fibrinogen receptor
Deficiency of GPIIa/IIIb (fibrinogen receptor) on surface of platelets causes which disease?
Glanzmans’ thrombasthenia
How is Glanzman’s thrombasthenia inherited?
AR
Bernard Soulier Syndrome is caused by what?
Absence of GPIb complex (VWF receptor) on platelet surface
Investigation findings with Bernard Soulier syndrome?
thrombocytopenia
large platelets
Markedly prolonged bleeding time (>20mins)
Features of Wiscott-Aldrich syndrome (4)?
Thrombocytopenia Tiny platelets Eczema Recurrent infections (5-15% develop lymphoreticular malignancies)
How is Wiscott-Aldrich inherited?
X-linked
What is Evan’s syndrome?
Rare syndrome where autoimmune haemolytic anaemia + ITP occur in the same patient
Drugs which cause platelet dysfunction include?
COX inhibitors: Aspirin, NSAIDs
Antibiotics: penicillin, cephalosporins
Heparin
Alcohol
