Week 10 Flashcards
What can disorders in primary hemostasis cause
-fatal chronic hemorrhage
-Blood vessel disorders (collagen abnormalities)
-Quantitative PLT disorders
-Qualitative PLT disorders
-Von Willebrand Disease
What is the role of platelets in primary hemostasis
where are they produced
-made from the cytoplasm of bone marrow megakaryocytes
-metabolically active
-initiate and control hemostasis
At time of injury they
-Adhere to site of injury
-aggregate to each other
-secrete granule contents
form a platelet plug
Adhering and activation of platelets
-adhere to no platelet surfaces like subendothelial collagen (in veins and capillaries) with GPIa/IIa and &GPVI (which are platelet receptors that bind to vascular collagen)
-vwf helps to link platelets to collagen in stressed areas like arterioles or arteries with GPIB/IX/V (platelet receptor that binds vwf)
-bind reversibly
-platelet changes shape
What is actin
stimulates transformation from discoid shape to spherical with pseudopods
What are platelets made from
-made from the cytoplasm of bone marrow megakaryocytes
What happens when platelets aggregate?
-bind to each to each other by the GPIIb/IIIa receptor complex activated by Thromboxane A2 & ADP
-they are also released into the environment to activate other PLTs
- GPIIb/IIIa receptor also allows the binding of Fibrinogen and VWF
-once fibrinogen binds the receptor it joins a neighboring PLT
-this is how the plt shape spreads
-irreversible
What does normal aggregation require?
- Intact platelet membrane
- Normal fibrinogen level
- Normal platelet granule secretion
- GPIIb/IIIa complex receptor
- ADP
- Thromboxane A2
Also needs Agonists that stimulate platelet aggregation
-adp
-Thromboxane A2
-Epinephrine
-Collagen
What do platelets secrete at the time of injury
-secrete alpha and dense granules during aggregation and adhesion
-have procoagulant secretion properties and release vwf, FVII, FV, and Fibrinogen
-control secretion properties of Protein S, PAI-1, a2-antiplasmin
-secret Ca, ADP
Thromboxane A2 - what does it cause
causes vasoconstriction and releases Ca2 to activate other platelets
LOOK AT THE CHARTS ON THE FOLLOWING SLIDES
How can PLT or Vascular abnormalities present:
-Qualitative or Quantitative
-congenital or acquired
-show as mucocutaneous bleeding , petechiae, purpura, ecchymosis,/bruising, epistaxis, gingival bleeding
What clinical states result in the quantitative plt disorder: Thrombocytosis
Reactive vs Myeloproliferative disorder
-increase platelet count over 450 x 10 ^9/L seen in
Reactive thrombosytosis – 2ndary
-after surgery, splenectomy, blood loss, IDA
-not associated with thrombosis or hemorrhage
-will disappear once the underlying condition is under control
Myeloproliferative disorder
-essential thrombocytopenia, Poly cythemia Vera, CML Primary Myelofibrosis
-causes thrombosis or bleeding
-marked and presistant elevations in PLT count
What is thrombocytopenia and how is it caused
PLT count of less than 150 x10^9
-common cause of significant bleeding
Causes
Impaired or decreased platelet production
-low BM megakaryocytes
-thrombopoiesis not working
Increased PLT destruction
-immune responses, mechanical damage, consumption or sequesteration
Abnormal Platelet distribution or dilution
-splenic sequestration due to splenomegaly – abnormal
-lowering of body temp or surgery with extracorporeal devices –transient decrease
-massive RBC transfusion and PLT are taken out of circulation
What is Fanconi Anemia
what do lab findings show
type of congenital thrombocytopenia
-genetic disorder characterized by aplastic anemia , physical abnormalities
-lab findings show
-HYPO cellular BM or BM failure
-pancytopenia however thrombocytopenia is seen first
-reticulocytosis
-macrocytosis on PBF
What does Fanconi Anemia present as
-short height
-pigmented skin
-petechiae
-bruising
-pale
-prone to infections
-bone and organ abnormalities
What is a hallmark disease of thrombocytopenia
-Acute Leukemia
-because the leukemic cells take over the BM
-only discovered because of the bruising
-low plt and rbc count
-WBC count is variable
What is bernard soulier syndrome
-disorder of PLT adhesion
-Autosomal recessive inheritance
-found in early childhood
-Ecchymosis, epistaxis, and gingival bleeding
-Missing or abnormally functioning GP Ib/IX/V receptor (PLT receptor that binds VWF)
-seen as giant plt
What is Glanzmann’s Thrombasthenia
Disorder of platelet aggregation:
-Platelets cant bridge with one another
-Platelet numbers and morphology are normal
-PLTs have defective or low levels of PLT GPIIb/IIIa (Fibrinogen & VWF) receptor
-Autosomal recessive disorder
-manifests in neonatal period or infancy
-rare coagulopathy
Glanzmann’s Thrombasthenia presentation
Increased mucosal bleeding
Menorrhagia
Easy bruising
Epistaxis
Gingival bleeding
Gastrointestinal bleeding
Post partum bleeding
Post-operative bleeding
-bleeding tendency is variable but can be severe
May-Hegglin Anomaly what is it
what is it seen as
-rare
-thrombocytopenia due to decreased production
-known as Giant PLT syndrome
on PBS
-Thrombocytopenia with Giant PLTs
-Basophilic inclusions - Dohle bodies in the cytoplasm of granulocytes and monocytes
-pts are asymp because PLTs have a normal function
-however if PLT count drops pts may have :
Epistaxis
Easy bruising
Gingival bleeding
Menorrhagia
What are storage pool defects - Dense granules
and examples
-congenital disorders
-divided into Albinism with or without
Arise from
-inability to package dense granule contents
-mutations of transporter or carrier -mediated systems that bring things into PLT dense granules
characterized by thrombocytopenia
Chediak-Higashi
Wiskott-Aldrich syndrome
Hermansky (Herman)-Pudlak
TAR syndrome
Chediak-Higashi Syndrome
storage pool defect - dense granules
-autosomal recessive
-granules in all cell lines look abnormal
-large lysosomal inclusions in WBCs-
Seen with
Albinism
Pancytopenia -Thrombocytopenia due PLT DENSE GRANULE DEFICIENCY
What is Wiskott-Aldrich Syndrome
and what is it characterized by
DENSE GRANULE DEFICIENCY
-x linked
-life threatening thrombocytopenia
-PLT abnormally small with decreased dense granules
characterized by
-Thrombocytopenia
-Eczema
-Immune deficiency - leading to recurrent bacterial infections
-Bleeding (secondary to Thrombocytopenia)
Hermansky (Herman)-Pudlak Syndrome what is it and what is it characterized by
DENSE GRANULE DEFICIENCY
-autosomal recessive
-arises due to mutations in genes that code for intracellular vesicular trafficking active organelle biogenesis
Characterized by
-albinism
-defective lysosomal function in many cells
-ceroid like deposits in cells of RES
-PLT dense granule def - PROFOUND
-bleeding is rare
-hemorrhage is lethal because of the dense granule def
-PLT morph is unique- marked dilation and twisting of SCCS = SWISS CHEESE PLT seen via electron microscope
Thrombocytopenia with absent radius syndrome (TAR) Syndrome
characterized by
DENSE GRANULE DEFICIENCY
-rare autosomal recessive
characterized by
-severe neonatal thrombocytopenia decreased production
-PLT dense granules have structural defects
-BM megakaryocytes may be decreased
- orthopedic abnormalities
-Congenital absence of the radial bones in the forearm
-cardiac abnormalities
What is Gray Platelet Syndrome and what is it characterized by
Deficiency of α-granules
-“Agranular” appearance of PLTs on PBS. They look grey
-PLT anisocytosis
-autosomal recessive inheritance
characterized by
-mucosal bleeding
-lifelong bleeding
-mod thrombo decreased production
-BM fibrosis with development of early myelofibrosis - Leukemia
-Giant grey PLTs
Increased Platelet Destruction
what categories is it separated into
Acquired Qualitative Platelet Disorders
Immune mechanisms
Caused by immunologic responses
Non-Immune mechanisms
Caused by mechanical damage,
consumption, or sequestration
In What ways does Immune-Mediated PLT Destruction happen
-AB form against PLT AG
-autoimmune system fail since AB are made against pt own PLT
-ALLO-immune - pt immune system is exposed to foreign platelets seen with PLT transfusion
-Drug induced - drug attaches to platelet surface seen as foreign and AB are produced against specific drug
What is Immune Thrombocytopenic Purpura (ITP)
Immune-Mediated PLT Destruction
-if acute -seen in children after viral infections or vaccinations
-if chronic -seen in adults, insidious
can be drug induced seen after use of cillin, ASA, CARBA, Heparin
Results
AB coated PLTs are removed from circulation and destroyed by REM
ITP mechanism of action
-AutoAB against PLT surface proteins GPIIb, GPIIIa, and/or GPIa/IIa are made
-AB coat platelets - forming immune complexes on PLT surface
-increase in splenic destruction by macrophages
Neonatal Immune Thrombocytopenias
Allo vs auto
Alloimmune
-mom has AB against baby platelet AG inherited from the father
-IgG AB crosses placenta, complexes with fetal PLT and thrombocytopenia results in fetus
Autoimmune
-mom has ITP or SLE, autoAB present
-passive transfer of autoAB across placenta causing abnormal complexes with fetal PLT and REM = thrombocytopenia
Secondary Thrombocytopenia
Immune Thrombocytopenias
Secondary Thrombocytopenia
-immune mediated
-assocaited with CLL, SLE or MALA
Post-Transfusion (Posttransfusion Purpura):
Immune Thrombocytopenias
-Patient transfused with products containing incompatible platelets & makes anti-PLT antibodies
-Antibodies cross-react with transfused PLTs and patient’s own PLTs, resulting in thrombocytopenia
Heparin-Induced Thrombocytopenia
Immune Thrombocytopenias
-side effect of heparin treatment that causes a reduced PLT count
-PT getting UFH for more than 5 days can develop IgG antibody specific for heparin–platelet factor complexes (platelet factor 4 complexed with heparin)
-pt on heparin need to have PLT count done every other day, a decrease in plt can indicate HIT
-immune complexes that are formed bind platelet Fc receptors, leading to:
Platelet activation
Thrombocytopenia
Microvascular thrombi
-Pts rarely bleed but have high risk of Thrombosis
-Venous thrombosis most common adverse effect
-Arterial thrombosis most serious adverse effect
Patients may develop:
Pulmonary emboli
Limb gangrene requiring amputation
Stroke
Myocardial infarction
Microangiopathic Hemolytic Anemias (MAHA)
non-Immune Thrombocytopenias
-life threatening hemolytic anemia which cause increase destruction of RBC and loss of PLT due to increased intravascular clotting where the PLT are consumed
-Formation of fibrin strands within the lumen of capillaries leads to formation of RBC fragments
-PBS of MAHA has many fragments with decreased PLT or thrombocytopenia
Three types of MAHA:
TTP
HUS
DIC
Thrombotic Thrombocytopenic Purpura (TTP)
Microangiopathic Hemolytic Anemias (MAHA)
non-Immune Thrombocytopenias
Characterized by
MAHA
Thrombocytopenia
Neurologic abnormalities
-accumulation of UL-VWF multimers in circulation due to def of ADAMTS13
-UL-VWF multimers are better at binding PLTs and do it spontaneously under stress
-PLT aggregates are formed in small blood vessels
-more thrombi or aggregates - the more platelets are consumed aka thrombocytopenia
Hemolytic Uremic Syndrome (HUS)
Microangiopathic Hemolytic Anemias (MAHA)
non-Immune Thrombocytopenias
-looks like TTP and is mostly in kids
Characterized by
MAHA
Thrombocytopenia
Renal failure
-2ndary complication to infection caused by S.dynsentreria or 0157:h7 due to Shiga toxin resulting in bloody diarrhea
-Toxins enter the blood stream and attach to renal glomerular capillary endothelial cells, which become damaged and release UL-VWF into local circulation
-Leads to thrombus formation in the kidneys and results in thrombocytopenia
-Thrombosis limited to kidney
Disseminated Intravascular Coagulation (DIC)
Microangiopathic Hemolytic Anemias (MAHA)
non-Immune Thrombocytopenias
Consumptive coagulopathy - because coag is activated due to increased tissue factor being exposed during sepsis or trauma
-quick consumption of FV, FVIII and Fibrinogen as clots form prolonging PT and APTT
-PLT are also consummed because they become trapped in the fibrin clots due to uncontrolled bleeding
-Characterized by MAHA and Thrombocytopenia
Abnormal PLT Distribution or Dilution can cause Thrombocytopenia example?
Splenic sequestration due to splenomegaly - abnormal sequestration
Lowering body temperature
Surgery with extracorporeal circulatory devices (transient decrease with dialysis or ECMO devices)
Loss from hemorrhage or surgery itself
Massive transfusion (or RBCs)- PLTs diluted out in circulation
Diagnosis of blood vessel disorders is often based on
Clinical symptoms
Family history of bleeding disorders
Laboratory tests that rule out platelet or coagulation disorders
Hereditary Hemorrhagic Telangiectasia
Vascular Disorders
-thin-walled BVs with discontinuous endothelium, inadequate smooth muscle and/or collagen/elastin as support - leading to bleeding (PLT unable to adhere and aggregate to vessel walls)
Paraprotenemia (Acquired Vascular disorder)
Vascular Disorders
Platelets are normal but function is impaired - PLT unable to adhere and aggregate during bleeding episodes due to
-Excess proteins (such as, myeloma proteins) or antibodies coat PLTs and their receptor functions are inhibited
-Coagulation factors are also unable to complex on coated PLT surface
Ehlers-Danlos Syndrome (hereditary vascular disorder)
Vascular Disorders
-inherited affecting collagen in body- skin, joints, BV
-seen as hyperextensible skin, hypermobile joints, joint laxity, and fragile tissues and Mucocutaneous bleeding
-Inadequacy of connective tissue causes defects in collagen production, structure, or cross-linking
Primary Hemostasis Testing: Platelet Function Tests
-Detect qualitative (functional) platelet abnormalities
-for pt who have mucocutaneous bleeding
-Hereditary platelet function disorders are rare
-Acquired defects are more common
-PLT count is done and PBF is reviewed first because thrombocytopenia is common cause of hemorrhage which you want to rule out first before doing PLT function testing
Platelet Aggregometry studies
Measure how well PLTs aggregate together to form clots
PFA-100 Analyzers
Automated platelet function testing
What is the PFA-100 Platelet Function Analysis
-analyzing platelet aggregation
-Citrated whole blood is aspirated at high rates in test cartridges
-the test cartridges have a membrane coated with a platelet agonist, Epinephrine, ADP or Collagen (point of adhesion) and an aperture
-Agonists induce platelet activation - adhesion and aggregation
-Time required for a PLT plug to occlude aperture is an indication of PLT function
-looks for inherited, acquired or drug induced plt dysfunction
-can be used for primary screening of Pt with hemostasis - VWD
-monitors DDAVP therapy in pre surgical pt
-assesses PLT dysfunction due to Aspirin
What is DDAVP
antidiuretic drug that releases VWF from the cells as a side effect to help with any mucocutaneous bleeding
what is Platelet Aggregometry
-measures how well PLTs aggregate to form clots
-sample procurement is very important as it must NOT activate plts. USE A LARGE BORE NEEDLE
-spin low for Platelet rich plasma
-let PLT regain function by letting sit 30 mins
-test within 4 hours of collection to avoid in vitro platelet activation and loss of normal activity
-Chilling destroys PLT activity - samples held at 15-25ºC until tested
What machines carry out Platelet Aggregometry
in 3 ways
Optical Aggregometry (uses PRP and a light-transmittance aggregometer)
Whole Blood Platelet Aggregometry (PLT aggregation measured by electrical impedance)
Platelet Lumiaggregometry (measures the amount of light produced when added to a blood sample)
this type of testing is high complexity and specialized
PLT Aggregometry- Optical Aggregometer test procedure
-prp in cuvette with stir bar and warm to 37
-photometer direct light through to photodetector
-OD of PRP is high
=baseline is 0% transmission - must establish
Add agonist (PLT activator or aggregating agent)
Platelet shape change – increase in %T
Platelets start aggregating – increase in %T
Platelets form large aggregate – up to 100%T
What are PLT agonist
-PLT activators which test different platelet activtion pathways or receptor function
-each agonist activates a different receptor and shows a different optical aggregometry tracing
Thrombin or synthetic TRAP
ADP
Epinephrine
Collagen
Arachidonic acid
Ristocetin - specific for VWF & PLT receptors
