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HAEMATOLOGY > PLATELET DISORDERS > Flashcards

PLATELET DISORDERS Flashcards

1
Q

What cells are platelets produced from?

A

Megakaryocytes in the bone marrow

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2
Q

Upon release from the bone marrow, where do young platelets travel to?

A

Spleen, where they are trapped for 36 hours before entering circulation

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3
Q

What is the normal lifespan of a platelet?

A

7-10 days

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4
Q

What is the normal platelet count for all age groups?

A

150-450 x10^9/L

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5
Q

What is the MPV (mean platelet volume)?

A

8-11 fL

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6
Q

What is a reticulated platelet?

A

A young platelet still containing RNA

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7
Q

Why is it useful to know about the proportion of platelets that are reticulated? What is the normal proportion?

A

Indirectly indicate state of marrow production

8-16%

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8
Q

What is the factor responsible for aiding platelet-endothelial cell adhesion?

A

von Willebrand factor

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9
Q

What is the factor responsible for aiding platelet-platelet adhesion?

A

Fibrinogen (factor I)

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10
Q

What is the glycoprotein found on the platelet membrane for which von Willebrand factor is the main binding protein?

A

Ib/IX complex

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11
Q

What is the glycoprotein found on the platelet membrane for which fibrinogen is the binding protein?

A

IIB/IIIa complex

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12
Q

What is contained within the intracellular dense granules of platelets?

A

Nucleotides
Calcium
Serotonin

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13
Q

What is contained within the intracellular alpha-granules of platelets?

A

Fibrinogen
von Willibrand factor
Platelet-derived growth factor
Clotting factors

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14
Q

How do platelets aid clotting in normal haemostasis?

A

Platelet aggregation forming platelet plugs
Release contents of granules
Provide an extensive phospholipid surface for interaction and activation of clotting factors in coagulation pathway

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15
Q

What is Fanconi’s anaemia?

A

Autosomal recessive preleukaemic condition which presents as thrombocytopenia. The cardinal laboratory feature is abnormal chromosomal fragility. Requires bone marrow transplant.

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16
Q

What is thrombocytopenia with absent radii?

A

TAR syndrome presents with the pathognomic sign of bilateral absent radii bones and with severe neonatal thrombocytopenia. Thrombocytopenia often improves after first year.

17
Q

What is Wiskott-Aldrich syndrome?

A

X linked disorder with a triad of thrombocytopenia, eczema and T-cell immunodeficiency. Requires bone marrow transplant.

18
Q

What is the most common cause of mild transient thrombocytopenia?

A

Viral infection

19
Q

What is the most common cause isolated thrombocytopenia (without anaemia or neutropenia)?

A

Idiopathic thrombocytopenia purpura - autoimmune disease

20
Q

What diseases is idiopathic thrombocytopenia purpura associated with?

A

SLE

Primary antiphospholipid syndrome

21
Q

Who is most likely to suffer from post-transfusion purpura?

A

Multiparous women who are negative for human platelet antigen.

22
Q

What is neonatal alloimmune thrombocytopenia?

A

Similar to haemolytic disease of the newborn but antigenic stimulus is from platelets not red cells.

23
Q

What drugs can be responsible for thrombocytopenia?

A

Heparin
Penicillamine
Cotrimoxadole

24
Q

What is the feature of heparin-induced thrombocytopenia?

A

Thrombosis causing thrombocytopenia

25
Q

What are the features of thrombotic thrombocytopenia purpura?

A

Clinical symptoms affecting any organ but primarily manifesting as neurological symptoms resulting from microvascular thrombosis.

26
Q

What is the underlying cause of thrombotic thrombocytopenia purpura?

A

Deficiency of ADAMTS 13

27
Q

How might someone with suspected thrombocytopenia present?

A 
Abnormal bleeding
Spontaneous skin purpura
Ecchymoses (bruise)
Mucous membrane bleeding
Prolonged nosebleeds
Menorrhagia
28
Q

What investigations should be ordered for someone with suspected thrombocytopenia?

A

FBC
Coagulation
Biochemical screen
Blood film

29
Q

How are congenital thrombocytopenias managed?

A

Filtered human leucocyte antigen compatible platelet transfusions
Desmopressin IV may work in minor episodes
Tranexamic acid
Recombinant factor VII may also prove useful
Bone marrow transplantation offers a cure

30
Q

How are acquired thrombocytopenias managed?

A

Filtered human leucocyte antigen compatible platelet transfusions

31
Q

How is life threatening childhood idiopathic thrombocytopenic purpura managed?

A

Corticosteroids

IV immunoglobulins

32
Q

How is adult idiopathic thromobocytopenic purpura managed?

A

Prednisolone and/or IV immunoglobulins

Rituximab in refractory patients

33
Q

How is someone with post-transfusion purpura managed?

A

IV immunoglobulin

Plasma exchange

34
Q

How is someone with thrombotic thrombocytopenic purpura managed?

A

Large volume plasma exchange
Aspirin
Avoid platelet transfusion

35
Q

How do you manage someone with DIC (disseminated intravascular coagulation)?

A

Fresh frozen plasma

Platelet transfusion

HAEMATOLOGY (17 decks)

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