4.1 - Primary hemostasis and related bleeding disorders

Question 1

platelets bind vWF using the _____ receptor

Answer 1

GPIb

Question 2

platelets bind _____ using the GPIb receptor

Answer 2

vWF

Question 3

where is vWF found?

Answer 3

• weibel palade bodies of endothelial cells

- alpha granules of platelets

Question 4

what is the role of ADP is platelet degranulation?

Answer 4

ADP promotes exposure of GPIIb / IIIa receptor on platelets

Question 5

TXA2 ____________ (promotes / inhibits) platelet aggregation

Answer 5

promotes

Question 6

ADP is released from platelet _____ granules

Answer 6

dense

Question 7

platelets aggregate at the site of injury via GPIIb / IIIa using _____________ as a linking molecule

Answer 7

fibrinogen

Question 8

what is the normal bleeding time?

Answer 8

2-7 minutes

Question 9

ITP is due to autoimmune production of _____ against platelet antigens?

Answer 9

IgG

Question 10

where are the autoantibodies against platelet antigens made in ITP?

Answer 10

plasma cells in the spleen

Question 11

what are the lab findings in ITP?

• platelet count
• normal PT / PTT
• megakaryocytes

Answer 11

• low platelet count
• normal PT / PTT
• high mega

Question 12

what is the initial treatment for ITP?

Answer 12

corticosteroids

Question 13

what is the treatment for ITP in cases of symptomatic bleeding? what is the rationale?

Answer 13

IVIG - to raise platelet count and defend patient’s platelets from being phagocytosed

Question 14

what is microangiopathic hemolytic anemia?

Answer 14

pathologic formation of platelet microthrombi in small vessels

Question 15

what type of RBC poikilocyte is seen in microangiopathic hemolytic anemia?

Answer 15

schistocyte

Question 16

microangiopathic hemolytic anemia is seen in what two conditions?

Answer 16

• HUS

- TTP

Question 17

TTP is due to decreased __________, an enzyme that normally cleaves vWF multimers into smaller monomers for eventual degradation

Answer 17

ADAMTS13

Question 18

what is the role of ADAMTS13?

Answer 18

cleaves vWF multimers into smaller monomers for eventual degradation

Question 19

what is the eventual result of decreased ADAMTS13 seen in TTP?

Answer 19

large, uncleaved multimers lead to abnormal platelet adhesion, resulting in microthrombi

Question 20

what is the cause of HUS? it is classically associated with what disease / toxin?

Answer 20

• endothelial damage by drugs or infection

- e. coli O157:H7 dysentery (e. coli verotoxin)

Question 21

what is the most important complication of HUS?

Answer 21

renal insufficiency

Question 22

what is the most important complication of TTP?

Answer 22

CNS abnormalities

Question 23

what are the lab findings in microangiopathic hemolytic anemia (HUS, TTP)?

• bleeding time
• normal PT / PTT
• blood smear findings
• megakaryocytes

Answer 23

• bleeding time: increased
• normal PT / PTT: normal
• blood smear findings: schisocytes (and anemia)
• megakaryocytes: increased

Question 24

what are the bone marrow findings in microangiopathic hemolytic anemia (HUS, TTP)?

Answer 24

increased megakaryocytes

Question 25

what is the treatment for microangiopathic hemolytic anemia (HUS, TTP)?

Answer 25

plasmapheresis and corticosteroids (particularly in TTP)

Question 26

beranrd-soulier syndrome is due to a genetic deficiency of _____, which leads to defective ____________

Answer 26

• GPIb

- platelet adhesion

Question 27

what is seen on blood smear in bernard soulier syndrome?

Answer 27

enlarged platelets

Question 28

glanzmann thrombocytopenia is due to a genetic deficiency of ______, which leads to defective ___________

Answer 28

• GPIIb / IIIa

- platelet aggregation

Question 29

in uremia, (adhesion / aggregation / both / neither) is / are impaired

Answer 29

both