Platelets Flashcards
lifespan and distribution of platelets
lifespan 9-10 days
distribution 1/3 in spleen, 2/3 in circulation
conditions associated with macrothrombocytes
ITP Bernard-Soulier May-Hegglin Montreal platelet syndrome Gray platelet syndrome
conditions associated with microthrombocytes
Wiskott-Aldrich
TAR
CMV infection
most common antigen involved in NAIT?
HPA1a (75%), others: HPA-5b
what is the risk of ICH in a baby with NAIT
10-20% - frequently occurs in utero
what antibodies should you screen for in NAIT?
HPA1, 3, 5 (and 4 if asian)
natural hx of NAIT?
recovery of platelet count by 2-3 weeks
treatment of NAIT?
platelet transfusion (try random donor, unmatched platelets first - can try washed maternal platelets if ineffective) IVIG 1g/kg/day x 1-3 days methylpred HUS goal of tx: platelets > 30-50 if ICH: platelets > 100
which usually causes the most severe thrombocytopenia, NAIT or neonatal autoimmune thrombocytopenia?
NAIT - usually < 50
with neonatal autoimmune thrombocytopenia, 10-15% have plts < 50 (including less risk of ICH)
what is the antigen target of autoantibodies in neonatal autoimmune thrombocytopenia?
usually GPIIB/IIIA or GPIb/IX complexes
duration of low platelets in neonatal autoimmune thrombocytopenia?
approx 3 weeks
how common is thrombocytopenia in down syndrome
85% of neonates with T21 will have low platelets
weak platelet activators
ADP
epinephrine
potent platelet activators
collagen
thrombin
role of glycoprotein GPIa/IIa integrin receptor on platelet cell surface?
to bind collagen, resulting in platelet activation
