normal platelet count
150-400k
thrombocytopenia count
less than 150k
impaired platelet production can be caused by….
incr platelet destruction can be caused by…
most common cause of accelerated platelet destruction
antibodies
-attacks pltlt when the drug binds to pltlt surface
most common acquired thrombocytopenia
IMMUNE thrombocytopenia [ITP]
ITP results fr
ITP MOA
platelets are coated w antibodies> spleen thinks they are foreign + destroys them w macrophages
platelets normally survive..
8-10 days
possibly causes of ITP
thrombotic thombocytopenic purpura [TTP]
-assoc w deficiency of ADAMTS13 enzyme
-w/o the enzyme, unusually large amt of vWF attach to pltlt
»>promotes aggregation
-clotting + bleeding occur at same time
-MEDICAL EMERGENCY
ADAMTS13
plasma enzyme
-breaks down the vWF clotting factr
vWF
von Willebrand clotting Factor
-most important protein-mediating platelet adhesion to damaged endothelial cells
TTP is often assoc w…
hemolytic uremic syndr
TTP is characterized by…
hemolytic anemia
Heparin Induced Thrombocytopenia [HIT]
HIT should be suspected if…
pltlt count falls by more than 50% or falls below 150k
major problem of HIT
venous thrombosis
-arterial thrombosis can occur too
HIT complications
- arterial vascular infarcs> necrosis, stroke, end-organ damage
symptoms of bleeding w HIT are ___ bc…
- pltlt RARELY drops below 20k
HIT develops ____ after heparin therapy
5-10 days
HIT MOA
PF4 binds to heparin> then binds to pltlt> pltlt activation> more PF4 released (pos feedback loop)> antibodies are made against PF4-heparin-pltlt complx> removed prematurely fr circultn> thombocytopenia + pltlt-fibrin thrombi
thrombocytopenia clinical manifestations
bleeding in mucosa examples
nosebleed + gingival bleeding