PLATELET DISORDERS Flashcards
What cells are platelets produced from?
Megakaryocytes in the bone marrow
Upon release from the bone marrow, where do young platelets travel to?
Spleen, where they are trapped for 36 hours before entering circulation
What is the normal lifespan of a platelet?
7-10 days
What is the normal platelet count for all age groups?
150-450 x10^9/L
What is the MPV (mean platelet volume)?
8-11 fL
What is a reticulated platelet?
A young platelet still containing RNA
Why is it useful to know about the proportion of platelets that are reticulated? What is the normal proportion?
Indirectly indicate state of marrow production
8-16%
What is the factor responsible for aiding platelet-endothelial cell adhesion?
von Willebrand factor
What is the factor responsible for aiding platelet-platelet adhesion?
Fibrinogen (factor I)
What is the glycoprotein found on the platelet membrane for which von Willebrand factor is the main binding protein?
Ib/IX complex
What is the glycoprotein found on the platelet membrane for which fibrinogen is the binding protein?
IIB/IIIa complex
What is contained within the intracellular dense granules of platelets?
Nucleotides
Calcium
Serotonin
What is contained within the intracellular alpha-granules of platelets?
Fibrinogen
von Willibrand factor
Platelet-derived growth factor
Clotting factors
How do platelets aid clotting in normal haemostasis?
Platelet aggregation forming platelet plugs
Release contents of granules
Provide an extensive phospholipid surface for interaction and activation of clotting factors in coagulation pathway
What is Fanconi’s anaemia?
Autosomal recessive preleukaemic condition which presents as thrombocytopenia. The cardinal laboratory feature is abnormal chromosomal fragility. Requires bone marrow transplant.
What is thrombocytopenia with absent radii?
TAR syndrome presents with the pathognomic sign of bilateral absent radii bones and with severe neonatal thrombocytopenia. Thrombocytopenia often improves after first year.
What is Wiskott-Aldrich syndrome?
X linked disorder with a triad of thrombocytopenia, eczema and T-cell immunodeficiency. Requires bone marrow transplant.
What is the most common cause of mild transient thrombocytopenia?
Viral infection
What is the most common cause isolated thrombocytopenia (without anaemia or neutropenia)?
Idiopathic thrombocytopenia purpura - autoimmune disease
What diseases is idiopathic thrombocytopenia purpura associated with?
SLE
Primary antiphospholipid syndrome
Who is most likely to suffer from post-transfusion purpura?
Multiparous women who are negative for human platelet antigen.
What is neonatal alloimmune thrombocytopenia?
Similar to haemolytic disease of the newborn but antigenic stimulus is from platelets not red cells.
What drugs can be responsible for thrombocytopenia?
Heparin
Penicillamine
Cotrimoxadole
What is the feature of heparin-induced thrombocytopenia?
Thrombosis causing thrombocytopenia
