section 4 - platelet and vascular disorders Flashcards
describe hereditary hemorrhagic telangiestasia
- hereditary vascular disorder
- vessel walls = single layer of EC -> fragile vessels
- telangiectasia - dilated superficial vessels BLANCHE UNDER PRESSURE
- increased bleeding
describe ehlers-danlos syndrome
- hereditary vascular disorder with hypermobile joints
- collagen disorders impacting platelet adhesion
what is the mechanism of action for allergic and drug-induced purpuras
- acquired vascular disorder
- antibody to vessel walls deposits and damages
describe Henoch-Schonlein Purpura
- usually child after upp resp. infection
- IgA deposits in vessels
- IgA deposits in kidney and damages nephron
Scurvy!
- vitamin C deficiency
- decrease synthesis of collagen = weak capillary walls
senile purpura!
- loss of collagen and subcut fat = loss of stability for veins
- vein rupture
describe the defect in Bernard-Soulier syndrome and its signature appearance
- lack of Gp1b
- adhesion disorder
- large platelets
- all normal aggregation except with ristocetin
describe the defect in type 1 vWF disease
- most common
- decreased amount of all multimers
- since low vWF = low F8 = impacting coag cascade
describe type 2 vWF disease
- decrease in high MW multimers
- possible inability to stabilize large multimers
describe type 3 vWF disease
all multimers of vWF absent
- either reduced synthesis or rapid breakdown
how are different types of vWF diseases differentiated
- vWF:Ag determining vWF presence in plasma
- RIPA determining platelet function based on platelet agglutination pt PRP and PLT
- vWF:Rco determining platelet function based on platelet agglutination pt plasma and donor PLT
list other platelet adhesion problems not described
- autoimmune disorders
- myeloproliferative disorders
- multiple myeloma/waldenstroms
- chronic liver disease
- drugs
describe Glanzmann’s Thrombasthenia
- disorder of aggregation
- platelets lack Gp2b3a
- PT/APTT normal since a platelet issue, not coag
- platelet aggregation only normal with Ristocetin
describe uremia
- toxins interfering ith platelet funciton
describe aspirin resistance
- 22% of patients become resistant to anti-platelet effect
- associated with thrombosis
- detected with platelet aggregation studies -> arachidonic acid curve
describe storage pool diseases generally
lack of platelet dense or alpha granules -> defect in release reaction
- abnormal aggregation
delta DPD
lack of dense granules
describe Hermansky-Pudlak syndrome
- channel system dilated
- dense granule deficiency
- swiss cheese platelets
- deficient release rxn
describe gray platelet syndrome
- marked decrease in alpha granules
- hypo or granular platelets
- effects platelet aggregation
describe Wiskott Aldrich Syndrom
- micro platelets
- decrease alpha and dense granules
- plt sequestration and decreased platelet count
- immunodeficiency disorder
- congenital hypoplasia
describe Chediak-Higashi platelet syndrome
- platelets lack normal dense granules
describe reactive thrombocytosis
normal body response to blood loss
how does myeloproliferative disorders impact platelets
thrombocytosis and high platelets
describe essential thrombocythemia
- bizarre and giant platelets
describe how may hegglin impacts platelets
ineffective thrombopoiesis w/ large bizarre platelets
describe the differences between chronic and acute ITP
- chronic: may see early manifestation of AIDS w/ fluctuating course
- acute: mostly kids with history of infection
list and describe the three mechanisms of drug induced immune effects
- true auto Ab development - not dependent on presence of the drug
- hapten - linkage of drug to platelet then Ab forms
- drug complex - drug and Ab bind then attach to platelets
describe HAT (heparin-associated thrombocytopenia)
direct non immune platelet activation
describe heparin induced thrombocytopenia (HIT)
patient with thrombosis put on heparin and develop antibody against platelet factor 4 - heparin complex
what is the difference between HIT and HITTS
HIT plt count doesn’t fall below 100
HITTS plt count falls below 20 w/ thrombosis
describe HITTS
- HIT Ab releases micro particles from platelets and initiates cascade
- low platelets and thrombosis
- Ab is against Pf4-heparin complex
- HIT Ab binds to heparan on the endothelial cell surface
and stimulates expression of tissue factor
true or false
in HIT and HITTS the Ab is only active in the presence of heparin
true
- pt taken off heparin to measure
which tests are used for HIT
- SRA (reference)
- PLT aggregation (HIPA): common
- immunoassay (ELISA): most common
describe HIPA test method for HIT
test for presenf of heparin-induced Ab in pt plasma (off heparin for 8 hours)
- normal donor PLTs + PPP + dilutions of heparin
describe neonatal alloimmune thrombocytopenia
mother is HPA-1a neg, baby is positive, mother develops Ab
- HPA-1a version of HDN
describe post transfusion purpura
- antibodies form to antigen recipiant is neg for (HPA-1a)
describe HELLP acronyms
- hemolysis
- elevated liver enzymes
- low platelet count
-> variant of preeclampsia
list etiology of HELLP
- intravascular platelet activation
- microvascular endothelial damage
- thromboxane A2 release
- vasospasm
- vascular lesions in multiple organs
describe thrombotic thrombocytopenic purpura
- endothelial cell injury and platelet thrombus forms
- either autoantibody to ADAMTD13 or inherited variant of ADAMTS13 deficiency
describe the clinical and lab findings of TTP
- hemolytic anemia
- thrombocytopenia
- fluctuating neurological dysfunction
- progressive renal disease
describe HUS findings and distinguishing characteristics
- resembles TTP but differentiated based on severity of renal failure and absence of neural symptoms
- typically occurs after acute infection
- findings: MAHA, thrombocytopenia, acute renal failure
