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BL/DD USMLE and Basics > BL- Platelet disorders > Flashcards

BL- Platelet disorders Flashcards

1
Q

4 events in the formation of a platelet plug

A

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

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2
Q

Platelet Precursor

A

Megakaryocyte in bone marrow

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3
Q

How long do platelets circulate

A

Bud off, circulate 7-10 days

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4
Q

TPO: thrombopoietin

A

main growth and maturation factor for megakaryocytes

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5
Q

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

A

4 events in the formation of a platelet plug

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6
Q
  • inhibits coagulation
  • prevents platelet aggregation
  • promotes clot breakdown
  • provides barrier to reactive elements in the vessel wall
A

Normal Endothelium:

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7
Q

main growth and maturation factor for megakaryocytes

A

TPO: thrombopoietin

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8
Q

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

A

platelet surface

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9
Q

Who attracts platelets well?

A

Von Willebrand factor

*Temporary bond between GPIb (platelet) and vWF

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10
Q

Granules of Plts

A

Dense Granules
Lysosomes
Alpha granles

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11
Q

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

A

Dense

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12
Q

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

A

New platelets

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13
Q

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

A

Plt Adhesion

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14
Q

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

A

Plt activation

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15
Q

Platelets are laced together through fibrinogen bridges

A

plt Aggregation

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16
Q

Locally, thrombin converts the fibrinogen to fibrin stabilizing

A

Fibrin formation

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17
Q

Thrombocytopenia

A

(decreased numbers of platelets)

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18
Q

Normal platelet count between

A

150,000-400,000/ul

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19
Q

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

A

Platelets 20–50,000

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

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20
Q
  1. Decreased production of platelets
  2. Increased destruction of platelets
  3. Distribution disorders (Increased sequestration of platelets due to splenomegaly)
  4. Dilution (massive transfusion)
A

Causes of Thrombocytopenia

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21
Q

Low platelets in the setting of pancytopenia

A

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

~Nutritional deficiencies (B12/Folate)

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22
Q

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

A

Infection- common cause of low platelets

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23
Q

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

A

Acute ITP

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24
Q

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

A

Chronic ITP ( by definition >12 months):

25
Q

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.

A

Idiopathic thrombocytopenic purpura (ITP)

26
Q 
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
A

Von Willebrand Disease

27
Q

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

A

Von Willebrand protein fx

28
Q

Carry Factor VIII

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

A

Von Willebrand protein fx

29
Q

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

A

Tests for von Willebrand’s Disease:

Screening test

30
Q

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

A

Types of von Willebrand’s Disease

31
Q

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

A

Tests for von Willebrand’s Disease:

32
Q

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

A

Type 2- Types of von Willebrand’s Disease

33
Q

measures amount of vW protein

A

Tests for von Willebrand’s Disease:

34
Q

Partial quantitative vWF deficiency. 70-80% cases

A

Type 1- von Willebrand’s Disease

35
Q

Almost complete absence vWF. Rare

A

Type 3- von Willebrand’s Disease

36
Q

Von Willebrand Disease Treatment - DDAVP

A

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
Q

Other platelet function disorders

A
  1. Congenital
  2. Drug induced ( aspirin, NSAIDs, Plavix)
  3. Uremia
  4. Liver disease
  5. Myeloproliferative disorders
38
Q

__________ from obvious trauma suggests local vascular defect

A

Brisk bleeding

39
Q

____________ is more likely a generalized hemostatic disorder

A

Prolonged or recurrent bleeding

40
Q

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

A

Sudden resumption of bleeding

41
Q

_________ suggests a more severe, generalized hemostatic disorder

A

Multiple site bleeding

42
Q

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 ________.

A

acquired

43
Q

Qualitative Platelet Disorders

A 
Von Willebrand disease (vWD)
Bernard-Soulier syndrome
gray platelet syndrome
 afibrogenemia
Glanzmann thrombasthenia
44
Q

Quantitative Platelet Disorders

A

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

45
Q

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.

A

quantitative

46
Q

the most common congenital bleeding disorder.

A

Von Willebrand disease (vWD)

47
Q

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.

A

Bernard-Soulier syndrome

48
Q

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

A

gray platelet syndrome

49
Q

leads to both primary (platelet plug formation) and

secondary (formation of cross-linked fibrin) hemostatic defects.

A

afibrogenemia

50
Q

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

A

Glanzmann thrombasthenia

51
Q

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

A

sequestration

52
Q

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

A

immune thrombocytopenic purpura (ITP)

53
Q

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

A

Alloimmune thrombocytopenia

54
Q

Other nonimmune-mediated

causes of thrombocytopenia include:

A

DIC, sepsis, thrombotic thrombocytopenic

purpura (TTP), and hemolytic uremic syndrome (HUS).

55
Q

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

A

Basic screening tests when evaluating excessive bleeding

56
Q

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

A

von Willebrand

57
Q

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

Fibrinogen level

A

Basic screening tests when evaluating excessive bleeding

58
Q

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

A

Basic screening tests when evaluating excessive bleeding

59
Q

APTT as a screening test for the intrinsic coagulation pathway

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

A

Basic screening tests when evaluating excessive bleeding

BL/DD USMLE and Basics (55 decks)

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