4.1 - Primary hemostasis and related bleeding disorders Flashcards
platelets bind vWF using the _____ receptor
GPIb
platelets bind _____ using the GPIb receptor
vWF
where is vWF found?
- weibel palade bodies of endothelial cells
- alpha granules of platelets
what is the role of ADP is platelet degranulation?
ADP promotes exposure of GPIIb / IIIa receptor on platelets
TXA2 ____________ (promotes / inhibits) platelet aggregation
promotes
ADP is released from platelet _____ granules
dense
platelets aggregate at the site of injury via GPIIb / IIIa using _____________ as a linking molecule
fibrinogen
what is the normal bleeding time?
2-7 minutes
ITP is due to autoimmune production of _____ against platelet antigens?
IgG
where are the autoantibodies against platelet antigens made in ITP?
plasma cells in the spleen
what are the lab findings in ITP?
- platelet count
- normal PT / PTT
- megakaryocytes
- low platelet count
- normal PT / PTT
- high mega
what is the initial treatment for ITP?
corticosteroids
what is the treatment for ITP in cases of symptomatic bleeding? what is the rationale?
IVIG - to raise platelet count and defend patient’s platelets from being phagocytosed
what is microangiopathic hemolytic anemia?
pathologic formation of platelet microthrombi in small vessels
what type of RBC poikilocyte is seen in microangiopathic hemolytic anemia?
schistocyte
microangiopathic hemolytic anemia is seen in what two conditions?
- HUS
- TTP
TTP is due to decreased __________, an enzyme that normally cleaves vWF multimers into smaller monomers for eventual degradation
ADAMTS13
what is the role of ADAMTS13?
cleaves vWF multimers into smaller monomers for eventual degradation
what is the eventual result of decreased ADAMTS13 seen in TTP?
large, uncleaved multimers lead to abnormal platelet adhesion, resulting in microthrombi
what is the cause of HUS? it is classically associated with what disease / toxin?
- endothelial damage by drugs or infection
- e. coli O157:H7 dysentery (e. coli verotoxin)
what is the most important complication of HUS?
renal insufficiency
what is the most important complication of TTP?
CNS abnormalities
what are the lab findings in microangiopathic hemolytic anemia (HUS, TTP)?
- bleeding time
- normal PT / PTT
- blood smear findings
- megakaryocytes
- bleeding time: increased
- normal PT / PTT: normal
- blood smear findings: schisocytes (and anemia)
- megakaryocytes: increased
what are the bone marrow findings in microangiopathic hemolytic anemia (HUS, TTP)?
increased megakaryocytes
what is the treatment for microangiopathic hemolytic anemia (HUS, TTP)?
plasmapheresis and corticosteroids (particularly in TTP)
beranrd-soulier syndrome is due to a genetic deficiency of _____, which leads to defective ____________
- GPIb
- platelet adhesion
what is seen on blood smear in bernard soulier syndrome?
enlarged platelets
glanzmann thrombocytopenia is due to a genetic deficiency of ______, which leads to defective ___________
- GPIIb / IIIa
- platelet aggregation
in uremia, (adhesion / aggregation / both / neither) is / are impaired
both
