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102 Cards in this Set

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Q: Define hemostasis.
-a process which maintains blood in the fluid, clot-free state within the vascular system and by which bleeding is stopped (by inducing a rapid and localized hemostatic plug at a site of vascular injury)
Q: What are the four major systems involved in hemostasis?
-blood vessels (endothelium), platelets, coagulations system and fibrinolytic system
Q: What are the three minor systems involved in hemostatsis?
-kinin system, serine protease inhibitors and complement system
Q: What are some examples of serine protease inhibitors?
-anti-thrombin III-neutralizes serine proteases vs. plasmin, thrombin and factors II, IX, X, XI, and XII
-alpha2-macroglobulin
-protein C
-protein S
Q: What is the general sequence of events in hemostasis?
-vasoconstriction -> primary hemostasis -> secondary hemostasis -> thrombus and antithrombotic events
Q: Describe the vasoconstriction stage of hemostasis.
-after injury there is arteriolar vasoconstriction due to reflex neuorgenic mechanisms and augmented by local secretion of factors such as endothelin (vasoconstrictor)
Q: Describe the primary hemostasis stage of hemostasis.
-platelets adhere to endothelium due to exposure of thrombogenic subednothelial ECM and become activated
-platelets release factors that recruit additional platlets to form a hemostatic plug
Q: Describe the secondary hemostasis stage of hemostasis.
-tissue factor (procoagulant factor from endothelium) is exposed at injury site, this acts in conjunction with the secrete platelet factors to activate coagulation cascade activating thrombin
-thrombin converts circulating fibrinogen to insoluble fibrin resuling in fibrin deposition, it also induces further platelet recruitment
Q: Describe the thrombus stage of hemostasis.
-polymerized fibrin and platelts aggregate to form a permanent plug, after this there are counterregulatory mechanisms (tissue plasminogen activator t-PA) that are set into motion to limit the hemostatic plug to the site of injury
Q: How is bleeding prevented in blood vessels?
-vasoconstriction, rerouting of blood flow, platlet plug formation, and activation of the coagulation system (extrinsic, intrinsic, common pathway)
Q: What properties do intact endothelium have?
-they are inert to platelets and coagulation factors and have antithrombotic properties and thrombotic factors
Q: What are the antithrombotic properties that endotheloium have?
-endothelial cells are able to maintain an environment conducive to liquid blood flow by mechanisms that block platelet aggregation and adhesion, interfere with the coagulation cascade and actively lyse blood clots
Q: Describe the antiplatlet effects of the endothelium.
-intact endothelium prevents platelts and plasma coagulation factors from meeting the highly thrmbogenic subendothelial ECM
-NO and endothelial prostacylcin (PGI2) prevent activated platelts from other sites of injury to bind to endothelium that is not injured
-endothelial cells also express adenosine diphosphatase, which degrades ADP and thereby contributes to the inhibition of platelet aggregation
Q: What are the functions of both NO and endothelial PGI2?
-both are potent vasodilators and inhibitors of platelet aggregation, synthesized by endothlelium, NO is also able to inhibit secretion and endothelial adherence
-synthesis is stimulated by a number of factors (thrombin and various cytokines)
Q: Describe the anticoagulant effects of the endothelium.
-mediated by membrane-associated heparin-like molecules and by thrombomodulin (thrombin receptor)
-also makes tissue factor pathway inhibitor which is a cell-surface protein that complexes and inhibits activated tissue factor VIIa and factor Xa molecules
Q: What role do the heparain-like molecules have on anticoagulation?
-they act indirectly, they are cofactors that interact with antithrombin III to inactivate thrombin, factor Xa and several other coagulation factors
Q: What role does thrombomodulin have on anticoagulation?
-acts indirectly, binds to thrombin, coverting it from a procaogulant to an anticoagulant capable of activating protein C
-activated protein C inhibits clotting by proteolytic cleaving factors Va and VIIIa, this requires protein S as a cofactor, activated protein C alos stimulates the release of tissue plasminogen activator (TPA)
Q: Describe the fibrinolytic effects of the endothelium.
-endothelial cells synthesize tissue-type plasminogen activator (t-PA), promoting fibrinolytic activation to clear fibrin deposits from endothelial surfaces
Q: What role does the glycocalyx coat on the endothelium surface have for antithrombosis?
-made of heparin sulfate, it coats the luminal surface, activates antithrombin III and inhibits thrombin activity
Q: What are the prothrombic properties of the endothelium?
-becomes prothrombotic with activities that affect platelets, coagulation proteins and fibrinolytic system
-make tissue thromboplastin which activates extrinsic coagulation pathway
-also have platelet receptors for factors I, V, VIII, X, XI, XII and XIII to promote clot formation
Q: Describe the platelet effects of the endothelium during prothrombosis.
-formation of von Willebrand factor (vWF) that aids in platelet adhesion to injured endothelial cells
-vWF is an essential cofactor for platelet binding to collagen and other surfaces
-vWF is a product of normal endothelium and megakaryocytes, it is not specifically synthesized after endothelial injury
Q: Describe the procoagulant effects that the endothelium has during prothrombosis.
-endothelial cells are also induced by bacterial endotoxin or by cytokines (TNF or IL-1) to synthesize tissue factor (thromboplastin) which activates the extrinsic clotting cascade
-by bindig factors IXa and Xa, endothelial cells further augment the catalytic activities of coagulation factors
Q: Describe the antifibrinolytic effects that the endothelium has during prothrombosis.
-endothelial cells also secrete inhibitors of plasminogen activator (PAIs) which depress fibrinolysis
Q: What role do GPIb (glycoprotein Ib) receptors have on prothrombosis?
-binds to vWF, platelets adhere to impaired endothelium, is a high affinity thrombin binding site for thrombin activation of platelets
Q: What substances is the endothelium responsible for synthesizing?
-endothelin, type IV collagen, vWF and tissue thromboplstin (vWF)
Q: What are the vital statistics of platelets?
-produced in bone marrow, has a life span of 9-12 days, is 2-4 u in diameter, normal range is 150,000-450,000/uL
Q: Describe the structure of platelets.
-are anucleate and composed of three distinct zones
Q: What are the three distinct zones of the platlet?
-peripheral zone has a glycocalyx
-Sol-Gel zone
-organelle zone
Q: Describe the peripheral zone platelets.
-has HLA and platelet specific antigens
-has glycoprotein Ib which binds vWF and glycoprotein IIb and IIIa which binds fibrinogen
-has receptors for ADP, epinephrine, serotonin and thrombin
-has platelet factors (PF3 and PF4)
-has binding sites for factors I, V, VIII, X, XI, XII and XIII
Q: Describe the Sol-Gel zone of platelets.
-microtubules are present such as thrombosthenin (which is a contractile protein), is responsible for pseudopodia formation, reorganization of organells and release reaction
-microfilaments are also present (such as actin and myosin), helps in maintaining the discoid shape
Q: Describe the organelle zone.
-has alpha granules, dense granules and dense tubular system
Q: What are the two different types of granules contained in platelets?
-have alpha granules and dense bodies (or delta granules)
Q: What types of proteins are found in alpha granules?
-have platelet specific proteins including: (1) platelet factor 4, (2) beta-thromboglobulin (BTG), (3) platelet-derived growth factor, (4) thrombospondin (TSP), and (5) chemotactic factor
-have plasma proteins as well including: (1) fibrinogen, (2) vWF, (3) factors V and VIII, and (4) fibronectin
Q: What are the contents of platelet dense body granules?
-contains adenine nucleotides (ADP and ATP), ionized Ca2+, histamine, serotonin and epinephrine
Q: Describe the dense tubular system.
-responsible for prostaglandin synthesis and calcium sequestration and release
Q: What happens after platelets come into contact with ECM?
-on contact with ECM, platelets undergo three general reactions: (1) adhesion and shape change, (2) secretion (release reaction), and (3) aggregation
Q: Describe platelet adhesion and shape change step after platelet contact with ECM.
-platelet adhesion is mediated by vWF interaction which acts as a bridge between platelet surface receptors (glycoprotein Ib with factor V and IX) and exposed collagen
-vWF-GPIb are the only interactions sufficiently strong to overcome the high shear forces of flowing blood
-changes from discoid shape to sphere
Q: What happens with genetic deficiencies of vWF or GPIb?
-called Bernard-Soulier syndrome, results in defective platelet adhesion and bleeding disorders
-is an autosomal recessive defect of GP1b
-exhibits mucocutaneous bleeds of varying degrees (gingival bleeds, purpura, menorrhagia) seen early in life
Q: Describe the secretion step after platelet contact with ECM.
-leads to release of both granule types soon after adhesion, this process initiated by binding of agonists to platelet surface receptors followed by an intracellular protein phosphorylation cascade
-thrombin induces release of both granules
Q: What is the importance of the secretion of dense body (delta granules)?
-important because Ca2+ is required in the coagulation cascade and ADP is a potent mediator of platelet aggregation (platelets adhering to other platelets)
-ADP also augments further ADP release from other platelets
-platelets activate and leads to surface expression of phospholipid complexes which provide critical nucleation and binding sites for Ca2+ coagulation factors in the intrinsic clotting pathways
Q: Describe the platelet aggregation step after platelet contact with ECM.
-follows adhesion and secretion, aggregation stimulated by ADP and thromboxane A2 (TxA2, a vasoconstrictor secreted by platelets)
-ADP and TxA2 set up an autocatalytic reaction leading to build-up of platelet to form primary hemostatic plug and activate thrombin
Q: What is the role of thrombin in the platelet aggregation step?
-binds to a platelet surface receptor (PARs) and along with ADP and TxA2, cuases further aggregation
-followed by platelet contraction creating an irreversibly fused mass of platelets (viscous metamorphosis) called the secondary hemostatic plug
-thrombin converts fibrinogen to fibrin within the platelet plug cementing the platelets in place
-thrombin is therefore essential for thrombi formation, it stimulates platelet release reaction
Q: What role does noncleaved fibrinogen have?
-cofactor in platelet aggregation, ADP cahgnes conformation of GPIIb-IIIa receptors so they can bind fibrinogen, fibrinogen then acts to connect multiple platelets together to form large aggregates
Q: Describe the relationship between PGI2 and TxA2.
-PGI is a potent vasodilator and inhbitis platelet aggregation, TxA2 is a potent vasoconstrictor and activates platelet aggregation
-the interplay between these is balanced mechanism for human platelet function
Q: How is the plug stabilized?
-fibrin is formed and deposited leading to stabilization and contraction, PF3 is necessary for activation of clotting factors (factor X), factors V and VIII bind to platelet membrane receptors
Q: How does aspirin work?
-used in patients at risk for coronary thrombosis, aspirin irreversibly acetylates and inactivates cyclooxygenase, largely due to its ability to black TxA2 synthesis
-constricts vessels and activates platelets, also inhibits the release reaction of granules
Q: Are erythrocytes and leukocytes found in hemostatic plugs as well?
-yes, leukocytes adhered to platelets via P-selectin and to endothelium using an number of adhesion receptors, this contributes to the inflammatory response
-thrombin also directly stimulates neutrophil and monocyte adhesion and generates chemotactic fibrin split products form the cleavage of fibrinogen
Q: Give a summary of the series of platelet events that occur.
-platelets adhere to ECM at sites of endothelial injury and become activated
-on activation, they secrete granule products (e.g. ADP) and synthesize TxA2
-platelets also expose phospholipid complexes that are important in the intrinsic coagulation pathway
-injured or activated endothelial cells expose tissue factor, which triggers the extrinsic coagulation cascade
-released ADP stimulates the formation of a primary hemostatic plug, which is eventually converted (via ADP, thrombin, and TxA2) into a larger, definitive, secondary plug
-fibrin deposition stabilizes and anchors the aggregated platelets
Q: What role do platelets have in hemostasis?
-help maintain vascular integrity, form plugs and stabilize plug via fibrin formation
-in terms of vascular integrity it nurtures endothelial cells through release of endothelial growth factor, it promotes vascular healing at site of endothelial loss by stimulating endothelial cell and smooth muscle cell migration in vessel wall
Q: what are the biochemical pathways involved in TxA2 and prostocyclin production?
-arachidonic acid -> cyclooxygenase -> endoperoxides -> thromboxase synthetase -> TxA2 (platelet aggregation)
-archidonic acid -> cycboxygenase -> endoperoxides -> thromboxase synthetase -> prostocyclin (inhibits platelet aggregation)
Q: Describe fibrinolysis activation.
-early coagulation factors, primarily factor XII secreted primarily by endothelical cells, tissue plasminogen/plasmogen activator (TPA) is release, this activates plasminogen and forms plasmin
-plasmin breaks down fibrin and fibrogen, fibrin split products (fibrin degradation products)
Q: What does an elevated platelet count show?
-thrombocytosis, may be physiologic (dehydration) or secondary to malignancy (splenectomy, iron deficiency anemia, CML)
Q: What does a DEC platelet count show?
-thrombocytopenia, may be due to (1) production problem in marrow, (2) destruction problem in peripheral blood, or (3) distribution problem (spleen sequestering platelets
Q: What is the use of the bleeding time (BT) test?
-best overall test to evaluate vessel and platelet function up to formation of platelet plug
-a prolonged BT may be due to vascular disorders (scurvy), thrombocytopenia, aspirin therapy, vWF disease
Q: How is a platelet aggregation test done.
-platelet rich plasma aggregates in vitro when provided with ADP, collagen, ristocetin and epinephrine
-ADP added to platelet rich plasma leads to aggregation (1st wave, phase I)
-platelets release their own ADP which leads to further aggregation (phase II)
-recorded as a % transmittance
-no biphasic response in platelet release disorders
Q: Why are BT test and platelet aggregation done?
-tests for platelet function
Q: What happens with platelet aggregation test after aspirin therapy?
-phase I response is normal but phase II is absent
Q: What happens with platelet aggregation test with ristocetin?
-normal platelet aggregate because vWF are found in normal levels, vWF platelets do not aggregate with ristocetin
-in Bernard Soulier syndrome see no aggregation due to lack of GPIb receptor
Q: What happens with platelet aggregation test with collagen?
-lag period is seen initially, only one wave of aggregation
Q: What happens with platelet aggregation test with epinephrine and thrombin?
-aggregation is biphasic
Q: What does platelet factor 3 do?
-is released in vitro when activated by stimulants (kaolin or celite)
-acts as parital thromboplastin which is needed for intrinsic conversion of prothrombin to thrombin
Q: What is the clinical symptom of platelet abnormalities?
-purpura
Q: Describe drug-induced thrombocytopenia.
-idiosyncratic, hypersensitivity and uncommon
-due to destruction of platelets after drug ingestion
-drugs most commonly involved are quinine, quinidine, sulfonamide antibotics and heparin
Q: Describe heparain induced thrombocytopenia (HIT).
-of particular importance because heparin is a widely used anticoagulant, occurs in approx. 5% of patients receiving heparin
-most likely results from a direct platelet-aggregating effect of heparin
-caused by an immune reaction directed against a complex of heparin and platelet factor 4, heparin binding modifies the conformation of platelet factor 4 making it susceptible to immune recognition
-binding of Ab to platelet factor 4 produces immune complexes that activate platelets, promoting thrombosis even in the setting of market thrombocytopenia
Q: Describe immune thrombocytopenia purpura (ITP).
-there is an acute form (in children, self-limited and a single episode in life) as well as a chronic form (in adults), have a normal spleen size
-autoimmune disorders in which platelet destruction results from the formation of antiplatelet Abs
-found in lupus, AIDS, after viral infections and as a complication of drug therapy
Q: Describe the pathogenesis of chronic ITP.
-caused by the formation of autoAbs against platelet membrane glycoproteins, most often IIb-IIIa or Ib-IX, in majority of the cases, the antiplatelet Abs are of the IgG class
Q: Describe the mechanism of platelet destruction in chronic ITP.
-similar to that seen in autoimmune hemolytic anemias, opsonized platelets are rendered susceptible to phagocytosis by the cells of the mononuclear phagocyte system
-the spleen is the major site of removal of sensitized platelets
-megakaryocytes may be damaged by autoAbs leading to impairment of platelet production
Q: What are the clinical features of chronic ITP?
-occurs most commonly in adult women younger than age 40 years, female:male is 3:1
Q: Describe acute immune thrombocytopenic purpura.
-caused by antiplatelet autoAbs, but its clinical features and course are distinct, equal frequency for girls and boys
-usually preceeded by viral illness, self-limited and resolves within 6 months
Q: Describe post-transfusion thrombocytopenia.
-dilutional (after 5 units), have anti-platelet Ab
-massive transfusions can produce a dilutional thrombocytopenia, blood stored for longer than 24 hours contains virtually no viable platelets, thus plasma volume and red cell mass are reconstituted by transfusion, but the number of circulating platelets is relatively reduced
Q: Describe neonatal thrombocytopenia.
-due to infection or maternal platelet Abs
Q: Describe hypersplenism thrombocytopenia.
-have splenomegaly and get sequestration of platelets
-thrombocytopenia may develop in any patient with marked spelnogmegaly called hypersplenism, spleen normally sequesters 30-40% of the body’s platelets, which remain in equilibrium with the circulating pool
-when necessary, hypersplenic thrombocytopenia can be ameliorated by splenectomy
Q: Describe thrombotic thrombocytopenia purpura (TTP).
-idiopathic extreme thrombocytopenia found in young adults with a femal preponderance
-has an unknown cause, is associated with a lack of vWF cleaving protein resulting in ultralarge multimers of vWF resulting in platelet aggregate
-also associated with clinical pentad
Q: What is the clinical pentad associated with TTP?
-thrombocytopenia, MAHA (macroangiopathic hemolytic anemia), transient neurologic defects, renal failure and fever
Q: What are the lab tests associated with TTP?
-coagulation tests (PT, aPTT) are normal (not a true consumptive coagulopathy)
Q: How is HUS differentiated from TTP?
-HUS is distinguished from TTP by the absence of neurologic symptoms, the prominence of acute renal failure, and frequent affliction of children
Q: What is the pathophysiology of TTP?
-common fundamental feature is widespread formation of hyaline thrombi, comprised primarily of platelet aggregates, consumption of platelets leads to thrombocytopenia and the intravascular thrombi provide a likely mechanism for the MAHA and widespread organ dysfunction
-absent in ADAMTS 13 enzyme (vWF metalloprotease) and it normally degrades very high molecular weight multimers of vWF
Q: What happens with the absence of ADAMTS 13?
-get very high MW multimers of vWF that accumulate in plasma and promote platelet microaggregate formation throughout the microcirculation leading to symptoms of TTP, plasma exchange can be life saving by providing the missing enzyme
Q: Describe disseminated intravascular coagulation (DIC).
-never a primary disease, always secondary (severe burns, massive crush injuries, malignancies (acute progranulocytic leukemia), is a consumptive coagulopathy, an induced pathologic intravascular coagulation
-PT and aPTT are INC, fibrin degradation products (FDPs) are present (positive D dimmers), DEC fibrinogen levels
-thrombocytopenia present
Q: What is associated with DIC?
-is a thrombohemorrhagic disorder occuing as a secondary complication in a variety of diseases
-characterized by activation of the coagulation sequence that leads to the formation of microthrombi throughout the microcirculation
-as a consequence of the thrombotic diathesis, there is consumption of platelets, fibrin and coagulation factors and secondarily activation of fibrinolytic mechanisms
-assocaited with pregnancy, shock, sepsis, malignancy
Q: How does DIC present?
-present with signs and symptoms relating to tissue hypoxia and infarction caused by microthrombi
Q: Describe the pathophysilogy of DIC.
-DEC could result form pathologic activation of the extrinsic and/or intrinsic pathways of coagulation or impairment of clot-inhibiting influences
-triggered by (1) release of tissue factor or thromboplastic substances into the circulation and (2) widespread injury to the endothelial cells
Q: What are the consequences of DIC?
-there is widespread deposition of fibrin within the microcirculation, this can lead to ischemia of the more severely affected organs and to a hemolytic anemia resulting from fragmentation of red cells (MAHA)
-a hemorrhagic diathesis can dominate the clinical picture, results from consumption of platelets and clotting factors as well as activation of plasminogen, fibrinolysis leads to the formation of fibrin degradation products which inhibit platelet aggregation and fibrin polymerization and have antithrombin activity
Q: What are the lab findings associated with DIC?
-prolong PT and aPTT
-MAHA (shistocytes)
-DEC platelets (consumption) and fibrinogen (consumption)
-INC fibrin degradation products (fibrinolysis), see D-dimer
Q: Describe bone marrow diseases and thrombocytopenia.
-marrow replacement (in malignancy-leukemia, myelofibrosis) and chemotherapy can cause thrombocytopenia
Q: What is the differential for thrombocytosis?
-malignancy, infection, splenectomy (bleeding disorders (compensatory) and iron deficiency anemia)
Q: Describe thrombocytosis.
-idiopathic (think bone marrow disorder), seen in CML and essential thrombocythemia
Q: Describe von Willebrand disease.
-frequency of 1%, one of the most common inherited disorders of bleeding in humans, transmitted as an autosomal dominant disorder
Q: How does von Willebrand disease manifest clinically?
-characterized by spontaneous bleeding from mucous membranes, excessive bleeding from wounds, menorrhagia and a prolonged bleeding time in the presence of a normal platelet count
-due to abnormality of factor VIII related protein (von Willebrand’s factor), get lack of platelet adhesion and abnormal platelet aggregation studies
-is the most common hereditary bleeding disorder (1-2% of general population afflicted)
Q: Describe Type 1 and type 3 von Willebrand disease.
-assocaited with a reduced quantity of circulating vWF, type 3 more severe than type 1, type 1 more common, in type 1 all vWF components are equally reduced but in type 3 very little to no vWF
-deficiency in vWF has a marked affect on stability of factor VIII, resemebles hemophilia
Q: Describe Type 2 von Willebrand disease.
-qualitative defects in vWF, autosomal dominant disorder due to missense mutations that forms abnormal vWF, have reduced high molecular weight multimers
Q: What are the lab findings associated with von Willebrand’s disease?
-have prolonged bleeding time despite a normal platelet count
-plasma level of active vWF is measured as the ristocetin cofactor activity is reduced
-prolonged aPTT
-DEC factor VII:C, vWF:ag, and vWF:activity
Q: What are the clinical manifestations of von Willebrand’s disease (pseudohemophilia)?
-episodic bleeding (GI tract, menorrhagia), bleeds with trauma and surgery, INC symptoms with aspirin consumption
Q: What is the affect of aspirin on platelet action?
-causes irreversible inactivation of platelet cyclo-oxygenase resulting in inhibition of TxA2 synthesis, leads to blocking of platelet aggregation
-inhibition occurs for entire life of platelets
Q: What affect do endothelial cells have on platelet action?
-cyclo-oxygenase does not yield TxA2 but rather PGI2 (prostacyclin), PGI2 is potent inhibitor of platelet aggregation and is a vasodilator
-aspirin inhibits cyclo-oxygenase production in endothelial cells, as aspirin levels DEC, organelles in endothelial cells can produce cyclo-oxygenase, high levels prevent cyclo-oxygenase production on platelets and endothelium
-this leads to INC chance of hemolysis
Q: Describe Bernard-Soulier syndrome.
-caused by an inherited deficiency (autosomal recessive) of the platelet membrane glycoprotein complex Ib-IX, this glycoprotein is a receptor for vWF and is essential for normal platelet adhesion to subendothelial matrix
-facilitates thrombin activation of platelets
Q: What are the clinical symptoms associated with Bernard-Soulier syndrome?
-early in life and DEC with age, have mucocutaneous bleeds of varying degree (gingival bleeds, purpura, epistaxis, menorrhagia, GI bleeds)
Q: What are the lab findings associated with Bernard-Soulier syndrome?
-thrombocytopenia with large, irregularly shaped platelets
-bone marrow yields normal number of megakaryocytes
-platelet aggregation (normal with ADP, epinephrine and collagen, DEC with ristocetin (acts on GPIb receptor, also seen in von Willebrand’s disease, corrected by normal plasma in vWD), normal vactor VII: C and vWF: Ag (bleeding time prolonged, normal clot retraction)
Q: Describe Glanzmann’s Thrombasthenia.
-bleeding due to defective platelet aggregation, autosomal recessive
Q: Describe the pathophysiology of Glanzmann’s Thrombasthenia.
-thrombasthenic platelets fail to aggregate in response to ADP, collagen, epinephrine and thrombin owing to deficiency or dysfunction of GPIIb-IIIa, leads to formation of bridges between by binding fibrinogen and vWF, get cross linking of fibrinogen leading to clot retraction
Q: What are the clinical symptoms associated with Glanzmann’s Thrombasthenia?
-easy and prolonged bleeding, gingival bleeding, menorrhagia, GI bleeds less common than Bernard-Soulier syndrome
Q: What are the lab findings associated with Glanzmann’s Thrombasthenia?
-normal platelet count with normal morphology
-absent platelet aggregating with ADP, epinephrine and collagne
-normal aggregation with ristocetin and vWF
-prolonged bleeding time and clot retraction