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Flashcards in BL- Platelet disorders Deck (59):
1

4 events in the formation of a platelet plug

Platelet adhesion
Platelet activation
Platelet aggregation
Fibrin formation and support of local coagulation

2

Platelet Precursor

Megakaryocyte in bone marrow

3

How long do platelets circulate

Bud off, circulate 7-10 days

4

TPO: thrombopoietin

main growth and maturation factor for megakaryocytes

5

Platelet adhesion
Platelet activation
Platelet aggregation
Fibrin formation and support of local coagulation

4 events in the formation of a platelet plug

6

-inhibits coagulation
-prevents platelet aggregation
-promotes clot breakdown
-provides barrier to reactive elements in the vessel wall

Normal Endothelium:

7

main growth and maturation factor for megakaryocytes

TPO: thrombopoietin

8

Glycoproteins on _____ are receptors for adhesive proteins present in the vessel wall and in plasma

platelet surface

9

Who attracts platelets well?

Von Willebrand factor

*Temporary bond between GPIb (platelet) and vWF

10

Granules of Plts

Dense Granules
Lysosomes
Alpha granles

11

_______granules release serotonin ( vasoconstriction) , ADP platelet activation, calcium (further activation, adhesions and aggregation) of other platelets

Dense

12

_________stick to activated platelets and are themselves activated through release of compounds that further amplify platelet activation

New platelets

13

Platelets adhere to damaged vessel wall directly via collagen or indirectly via von Willebrand factor

Plt Adhesion

14

Excitatory agonists (collagen, thromboxane A2, etc.) cause a conformational change in platelet to expose Glycoprotein IIbIIIa binding sites for fibrinogen

Plt activation

15

Platelets are laced together through fibrinogen bridges

plt Aggregation

16

Locally, thrombin converts the fibrinogen to fibrin stabilizing

Fibrin formation

17

Thrombocytopenia

(decreased numbers of platelets)

18

Normal platelet count between

150,000-400,000/ul

19

may see spontaneous hemorrhage and increased risk of hemorrhage with trauma or surgery

Platelets 20–50,000

*Platelets <10,000-20,000: can see life-threatening spontaneous hemorrhage

20

1. Decreased production of platelets
2. Increased destruction of platelets
3. Distribution disorders (Increased sequestration of platelets due to splenomegaly)
4. Dilution (massive transfusion)

Causes of Thrombocytopenia

21

Low platelets in the setting of pancytopenia

~In the elderly think of Myelodysplastic syndrome (high MCV) and other hem malignancies (non-Hodgkin’s Lymphoma)

~Nutritional deficiencies (B12/Folate)

22

Very common cause of low platelets
Can be seen in bacterial and viral infections
Viral: HIV, hepatitis C

Infection- common cause of low platelets

23

Disease of children or young adults following viral infection
Sudden onset severe thrombocytopenia with petechiae and nosebleeds
Recovery in 2-6 weeks without treatment or after steroids

Acute ITP

24

Adults
Often have concurrent autoimmune disorders (e.g. SLE, RA), lymphoma, or HIV, though most cases idiopathic
Primary ITP is therefore a diagnosis of exclusion
Treatment options include steroids, IVIG, splenectomy, TPO receptor agonists

Chronic ITP ( by definition >12 months):

25

a disorder that can lead to easy or excessive bruising and bleeding. The bleeding results from unusually low levels of platelets — the cells that help your blood clot.

Idiopathic thrombocytopenic purpura (ITP)

26

Most common congenital bleeding disorder
Usually autosomal dominant
Abnormality in platelet/endothelial interaction
Clinical problems:
Mucosal bleeding
Nose bleeds
GI bleeds
Menorrhagia
Bleeding after surgery if no correction

Von Willebrand Disease

27

Adhere platelets to exposed collagen that acts as scaffolding for vWF at the site of a wound or vessel disruption

Von Willebrand protein fx

28

Carry Factor VIII
Without this protein, Factor VIII has a VERY short half-life

Von Willebrand protein fx

29

Platelet Function Analyzer (PFA) (measures 1st function of the vW protein)

Tests for von Willebrand’s Disease:
Screening test

30

Type 1: Partial quantitative vWF deficiency. 70-80% cases

Type 2: Qualitative defects – either decreased (2A) or increased (2B) adhesion to platelets with latter accelerating vWF clearance. 15-30% cases

Type 3: Almost complete absence vWF. Rare

Types of von Willebrand’s Disease

31

Factor VIII level normal or decreased (measures 2nd function of vW protein)

Tests for von Willebrand’s Disease:

32

Qualitative defects – either decreased (2A) or increased (2B) adhesion to platelets with latter accelerating vWF clearance. 15-30% cases

Type 2- Types of von Willebrand’s Disease

33

measures amount of vW protein

Tests for von Willebrand’s Disease:

34

Partial quantitative vWF deficiency. 70-80% cases

Type 1- von Willebrand’s Disease

35

Almost complete absence vWF. Rare

Type 3- von Willebrand’s Disease

36

Von Willebrand Disease Treatment - DDAVP

DDAVP (arginine vasopressin) enhances already synthesized vWF release from endothelial stores so effective in type 1 but not type 2 or type 3 disease

37

Other platelet function disorders

1. Congenital
2.Drug induced ( aspirin, NSAIDs, Plavix)
3. Uremia
4. Liver disease
5. Myeloproliferative disorders

38

__________ from obvious trauma suggests local vascular defect

Brisk bleeding

39

____________ is more likely a generalized hemostatic disorder

Prolonged or recurrent bleeding

40

___________ from injured site raises the possibly of excessive fibrinolysis or abnormal crosslinking of fibrin

Sudden resumption of bleeding

41

_________ suggests a more severe, generalized hemostatic disorder

Multiple site bleeding

42

Disorders can be classified as either qualitative (abnormal function) or quantitative (not enough or too
many platelets). They can be further classified as congenital or ________.

acquired

43

Qualitative Platelet Disorders

Von Willebrand disease (vWD)
Bernard-Soulier syndrome
gray platelet syndrome
afibrogenemia
Glanzmann thrombasthenia

44

Quantitative Platelet Disorders

immune thrombocytopenic purpura (ITP)
Alloimmune thrombocytopenia
DIC, sepsis, thrombotic thrombocytopenic
purpura (TTP), and hemolytic uremic syndrome (HUS)

45

Disorders can be classified as either qualitative (abnormal function) or _____(not enough or too
many platelets). They can be further classified as congenital or acquired.

quantitative

46

the most common congenital bleeding disorder.

Von Willebrand disease (vWD)

47

a rare autosomal recessive disorder where expression of GP1b on the platelet surface is reduced, leading to a defect in platelet adhesion. Platelet aggregation studies only show abnormal aggregation with ristocetin.

Bernard-Soulier syndrome

48

Storage pool deficiencies can occur, with a deficiency of either dense granules or α-granules. Deficiency of α-granules is known as

gray platelet syndrome

49

leads to both primary (platelet plug formation) and
secondary (formation of cross-linked fibrin) hemostatic defects.

afibrogenemia

50

rare autosomal recessive bleeding disorder caused by absent or defective GPIIb-IIIa

Glanzmann thrombasthenia

51

Thrombocytopenia (a low platelet count) can be due to decreased platelet production, increased platelet destruction or consumption, or _______ of platelets in the spleen.

sequestration

52

The most common cause of thrombocytopenia due to increased destruction is:

immune thrombocytopenic purpura (ITP)

53

occurs when a patient develops antibodies to platelet antigens not present on the patient’s own platelets

Alloimmune thrombocytopenia

54

Other nonimmune-mediated
causes of thrombocytopenia include:

DIC, sepsis, thrombotic thrombocytopenic
purpura (TTP), and hemolytic uremic syndrome (HUS).

55

Platelet count and blood smear to evaluate for thrombocytopenia or other hematologic
abnormalities

Basic screening tests when evaluating excessive bleeding

56

Mild cases of ______disease may require repeated testing to establish a diagnosis if clinical suspicion remains.

von Willebrand

57

Thrombin clotting time (TCT) to evaluate for fibrinogen defects, the presence of fibrin split products, or heparin effects

Fibrinogen level

Basic screening tests when evaluating excessive bleeding

58

Bleeding time or platelet function analyzer (PFA-100) to evaluate primary hemostasis

Basic screening tests when evaluating excessive bleeding

59

APTT as a screening test for the intrinsic coagulation pathway

PT/INR as a screening test for the extrinsic coagulation pathway

Basic screening tests when evaluating excessive bleeding