Primary Hemostasis and Related Disorders

Question 1

First step in 1˚ hemostasis

Answer 1

vasoconstriction

Question 2

Vasocontriction in 1˚ hemostasis is mediated by

Answer 2

endothelin from damaged cell

neural reflex

Question 3

Primary hemostasis step after vasconstriction

and its source

Answer 3

vWF binds exposed collagen

vWF from Weibel-Palade bodies in endothelial cells and α-granules of platelets

Question 4

vWF

origin and function

Answer 4

from Weibel-Palade bodies in endothelial cells and α-granules of platelets
vWF binds exposed collagen
platelets then bind vWF via GPIb
platelet adhesion

Question 5

After platelets bind vWF via GPIb, platelets release

Answer 5

ADP, Ca2+, and TXA2 released from platelets

Question 6

Function of ADP in 1˚ hemostasis

Answer 6

ADP binding receptor
induces GpIIb/IIIa expression on platelet surface
GpIIb/IIIa promotes adhesion with other platelets

Question 7

How does uremia affect platelet function

Answer 7

impairs both adhesion and aggregation

Question 8

Immune thrombocytopenia

defect

Answer 8

IgG Ab to GpIIb/IIIa
splenic macrophage consumption of platelets
*Ab are made in spleen and platelets are consumed in spleen

Question 9

Most common overall cause of thrombocytopenia in adults and children

Answer 9

immune thombocytopenia

usually due to viral illness

Question 10

Tx of immune thrombocytopenia

Answer 10

steroids
IVIG to stop acute attacks
splenectomy in refractory (usually adults)

Question 11

Mechanism of IVIG in immune thrombocytopenia

Answer 11

splenic macrophages consume IVIG instead of IgG-covered platelets
IgG to GpIIb/IIIa

Question 12

Petechiae are common sign of

Answer 12

platelet bleeding

usually quantitative defect

Question 13

TTP pathology

Answer 13

ADAMTS13
vWF metalloprotease
cleaves vWF multimers
cannot degrade vWF multimers, leading to microangiopathic hemolytic anemia

Question 14

Labs in TTP

Answer 14

schistocytes and elevated LDH

Question 15

Sx in TTP

Answer 15

neurologic Sx
renal
fever
thrombocytopenia
microangiopathic hemolytic anemia

Question 16

Tx of TTP

Answer 16

plasmaphoresis, steroids

Question 17

Inciting event in TTP

Answer 17

often autoimmune, antibody to ADAMTS13

or genetic

Question 18

Pathology of HUS

Answer 18

Shiga-toxin-producing E coli

STEC ie O157:H7

Question 19

Triad of HUS

Answer 19

thrombocytopenia
microangiopathic hemolytic anemia
acute renal failure

Question 20

Bernard-Soulier syndrome

pathology

Answer 20

GpIb deficiency
defect in platelet-to-vWF binding
large platelets, inability to form platelet plug

Question 21

Glanzmann thrombasthenia

pathology

Answer 21

GpIIb/IIIa deficiency

platelet aggregation decreased

Question 22

Lab findings in Glanzmann

Answer 22

no platelet clumping