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Exam 1
Chapter 31: Disorders of Primary Hemostasis
159
Science
Graduate
02/25/2013

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Term
Thrombocytopenia
Definition
decrease in the number of platelets in the peripheral blood below the reference range for an individual laboratory
Term
Thrombocytosis
Definition
an increase in the number of platelets in the peripheral blood above the reference range for an individual laboratory
Term
expected platelet count in thrombocytopenia
Definition
below 150 x 10^9/L
Term
expected platelet count in thrombocytosis
Definition
over 450 x 10^9/L
Term
Petechiae
Definition
(< 3mm) are small, pinhead-sized purple spots causes by blood escaping from capillaries into intact skin. These are associated with platelet and vascular disorders
Term
Purpura
Definition
(3mm-1cm) are purple discolorations of the skin caused by petechiae and/or ecchymoses
Term
Ecchymosis
Definition
(> 1cm) are bruises (bluish-black discoloration of the skin) that is larger than 3mm in diameter caused by bleeding from arterioles into subcutaneous tissues without disruption of intact skin
Term
Hematomas
Definition
localized collections of blood under the skin or in other organs caused by a break in the wall of the blood vessel
Term
Easy bruisability
Definition
is a common manifestation in disorders of primary hemostasis. Bruises usually appear on trunk without recognized trauma. Easy bruisability can also be associated with excessive and prolonged bleeding from cuts.
Term
Laboratory tests that can be ordered to screen for abnormalities of the hemostatic system
Definition
screening tests like PT, APTT, quantitative platelet count, BT, and fibrinogen assay
Term
expected clinical consequences when a patient has an abnormality of platelets or blood vessels
Definition
petechiae, ecchymoses, epistaxis (nose bleed), excessive bleeding from superficial wounds, bleeding into retina, gastrointestinal bleeding, bleeding in the urinary tract, hypermenorrhea, gingival bleeding (gums), increased bleeding after tooth extraction, and intracranial bleeding.
Term
Increased platelet counts correlation with disease maniestations
Definition
can be due to primary thrombocytosis (megakaryocyte proliferation and maturation bypass regulatory mechanisms, plt > 1000 x 103/ µL, seen in chronic myeloproliferative disorders), secondary thrombocytosis (reactive, increase in platelets caused by another disease, plt > 1000 x 103/ µL), or transient thrombocytosis
Term
decreased platelet counts correlation with disease manifestations
Definition
can be due to increased destruction of platelets which can be immune or non immune or decreased production of platelets which can be due to megakaryocyte hypoplasia (bone marrow), replacement of normal marrow (transplant), ineffective thrombopoiesis, or inherited disorders. Thrombocytopenia can also be due to increased splenic sequestration (90% of platelets held in spleen), dilutional thrombocytopenia (due to massive transfusions) or conditions with multiple mechanisms of thrombocytopenia
Term
Hematologic disorders characterized by thrombcytopenia
Definition
idiopathic immune thrombocytopenia, neonatal alloimmune thrombocytopenia, drug-induced thrombocytopenias, heparin associated thrombocytopenia, heparin induced thrombocytopenia or secondary to collagen diseases, autoimmune diseases, lymphoporliferative disorders, infections or vaccines. Thrombocytosis can also be related to disseminated intravascular coagulation, thrombotic thrombocytopenic purpura, hemolytic uremic syndrome and mechanical destruction.
Term
Hematologic disorders characterized by thrombocytosis
Definition
Thrombocytosis is seen in chronic myeloproliferative disorders and myelodysplasia, reactive thrombocytosis (malignancies, chronic inflammation, IDA, or hemolytic anemia)
Term
Immune mediated Thrombocytopenia etiology
Definition
platelets which are sensitized by antibody are removed by splenic macrophages in the spleen
Term
Immune mediated Thrombocytopenia pathophysiology
Definition
caused by antibodoies which sensitize the platelets
Term
Immune mediated Thrombocytopenia laboratory findings
Definition
Mean platelet volume and platelet count are used to evaluate platelets (high MPV with decreased plt count). Bone marrow shows increased megakaryocytes with increased ploidy.
Term
Etiology of ITP
Definition
auto reactive antibodies bind to platelets via receptors which shortens their life span
Term
Pathophysiology of ITP
Definition
idiopathic thrombocytopenia, autoimmune disorder
Term
Laboratory findings of ITP
Definition
Peripheral blood shows increased reticulated platelets, an increased in thrombopoetin. Can be chronic (seen in adults), acute (seen in children) or transplacental (newborns of mothers with ITP).
Term
Etiology of Neonatal alloimmune thrombocytopenia
Definition
maternal antibodies produced against fetal platelets (HPA-1a) that baby inhereited from father and mother lacks
Term
Pathophysiology of Neonatal alloimmune thrombocytopenia
Definition
platelet destruction by alloantibodies stimulated by foreign antigens during pregnancy or after blood transfusions
Term
laboratory findings of Neonatal alloimmune thrombocytopenia
Definition
high mortality rate due to bleeding into the CNS, bone marrow aspirations evaluates megakaryocytes and rules out other causes of thrombocytopenias, increased, markedly relfecting stimulation by TPO to increase platelet production, MPV is increased, PBS has increased platelets, normal TPO levels
Term
Etiology of Drug-induced thrombocytopenias
Definition
Heparin associated thrombocytopenia: non immune mediated in which heparin causes direct activation of plateletsHeparin induced thrombocytopenia: immune mediated in which heparin dependant platelet activating IgG against PF4 is bound by antibody an attached to platelet surface via platelets FcGamma receptors, causes an increase in platelet clearance.
Term
Pathophysiology of Drug-induced thrombocytopenias
Definition
generalzied hemoatopoietic supression, decrease in platelet production, increased destruction of platlets with cirulating immunoglobulins
Term
Laboratory findings of Drug-induced thrombocytopenias
Definition
very low platelet count, bleeding, withdrawl of drug reduces symptoms
Term
Etiology of Megakaryocyte hypoplasia
Definition
failure of bone marrow to deliver adequate platelets to the peripheral blood
Term
Pathophysiology of Megakaryocyte hypoplasia
Definition
due to drug or radiation therapy for malignant disease (decreased megakaryocyte syndromes), or pancytopenia and bone marrow hypoplasia (aplastic anemia
Term
Laboratory findings of Megakaryocyte hypoplasia
Definition
decreased platelet count appears before hypoplasia of other cell lineages, last lineage to return to normal, normal MPV, increased PDW (variation in size), increased TPO = aplasic anemia
Term
Primary malinant thrombocytosis
Definition
issue with megakaryocyte proliferation and maturation which bypasses the normal regulatory mechanisms, seen in chronic myeloproliferatative disorders and myelodysplasia.
Term
Secondary reactive thrombocytosis
Definition
an increase in platelets due to another disease or condition
Term
Effect of aspirin on platelets
Definition
Aspirin impairs acetylation and irreversible inhibition of platelet COX-1 which effects the platelet for its lifetime. It acetylates COX-1 in endothelial cells which blocks synthesis of PGI2 which affects the ability of the platelets to aggregate.
Term
What is the duration of asprin effects on platelets
Definition
the platelets entire lifetime, 7-10 days
Term
Bernard Soulier Syndrome clinical features
Definition
bleeding symptoms in homozygotes
Term
Bernard Soulier cause of clinical features
Definition
cause of large platelets is unknown, quantitative decrease or abnormal function of the GPIb/IX complex from mutation in gene that codes for proteins in GP complexes, lack of functional GPIb/IX complex prevents interaction of the platelets with vWF and the subsequent platelet adhesion to collagen
Term
Bernard Soulier laboratory features
Definition
moderate to severe thrombocytopenia, large platelets with uneven distribution, prolonged BT, normal platelet aggregation with ADP, collagen and epinephrine, abnormal platelet aggregation with ristocetin and VWF
Term
Glanzmanns thrombasthenia clincial features
Definition
bleeding problems in homozygotes
Term
Glanzmanns thrombasthenia cause of clincal features
Definition
defective GPIIb/IIA complex, platelet aggregation does not occur because platelets lack the site for attachment of fibrinogen, adhesion and secretion are normal
Term
Glanzmanns thrombasthenia laboratory features
Definition
prolonged BT, abnormal platelet aggregation in response to ADP, collagen, thrombin, and epinephrine, normal aggregation in response to ristocetin and VWF
Term
Delta storage pool disease clinical features
Definition
bleeding diathesis
Term
Delta storage pool disease cause of clinical features
Definition
platelet aggregation abnormalities are due to the lack of ADP release from the DG so that secondary aggregation does not occur with ADP or epinephrine
Term
Delta storage pool disease laboratory features
Definition
prolonged BT, second wave of aggregation with ADP and EPI but absent with collagen
Term
Alpha storage pool disease clinical features
Definition
gray platelets, bleeding diathesis
Term
Alpha storage pool disease cause of clinical features
Definition
defect in targeting endogenously synthesized proteins to the developing alpha granules
Term
Alpha storage pool disease laboratory features
Definition
mild thrombocytopenia with prolonged BT, platelet aggregation studies are normal (as opposed to delta storage disease)
Term
Thrombocytopenias due to increased destruction
Definition
immune destruction = ITP, NAIT, drug-induced thrombocytopenias (HIT and HAT), miscellaneous immunne thrombocytopenia, non-immune thrombocytopenia
Term
Thrombocytopenias due to decreased production
Definition
megakaryotcyte hypoplasia
Term
Primary thrombocytosis
Definition
chronic myeloproliferative disorders and myelodysplasia
Term
Secondary thrombocytosis
Definition
reactive thrombocytosis in which the increase in platelets is caused by another disorder or condition
Term
Transient thrombocytosis
Definition
spikes and the returns to normal, childbirth
Term
ITP etiology
Definition
immune destruction by autoreactive antibodies
Term
ITP pathophysiology
Definition
autoreactive antibodies to GPIIb-IIIa, GPIb-IX-V, and GPIa-IIa, bind to platelets and cause a shortened life span
Term
ITP laboratory findings
Definition
increased reticulated platelets (can be decreased if autoantibodis impede megakaryocyte differentiaion and platelet release), TPO can be normal to slighty increased, platelet count less than 20x 10^9/L, increased lymphocytes or mild eosinophilia, marrow shows normal or increased megakaryocytes
Term
NAIT etiology
Definition
alloimmune thrombocytopenia, 1st pregnancy
Term
NAIT pathophysiology
Definition
maternal antibodies produced agaisnt epitopes of paternal HPA-1a antigens on fetal platelets
Term
NAIT laboratory findings
Definition
low platelet count
Term
Drug-induced thrombocytopenia Etiology
Definition
drugs, generalized hematopoietic supression, selective suppression of platelet production or increased platelet destruction via IgG coated platelets
Term
Drug-induced thrombocytopenia pathophysiology Hapten theory
Definition
penicillin binds to platelets causing drug-platelet antigen complex and the drug-dependenet antibody binds to complex.
Term
Drug-induced thrombocytopenia laboratory findings of HIT
Definition
increased platelet clearance
Term
Drug-induced thrombocytopenia pathophysiology innocent bystander mechanism-HIT
Definition
Heparin binds to plasma protein (PF4)and the antibody response binds to the heparin, the immune complex nonspecifically binds to circulating platelets via Fc portion of antibody which binds to IgG FcGammaIIa receptor
Term
Drug-induced thrombocytopenia pathophysiology Drug-dependent antibody against epitopes
Definition
epitopes created by assocition of quinidine with proteins on platelet surface, quinidine binds on platelet surface via GPIb/IX or GPIIb/IIIa and leads to production of neoepitpopes
Term
HAT etiology
Definition
non-immune mediated mechanism
Term
HAT pathophysiology
Definition
heparin causes direct platelet activation which causes thrombocytopenia
Term
Miscellaneous Immune Thrombocytopenia Etiology
Definition
secondary to collagen dieases, autoimmune duseases, lymophoroliferative disorders, and infections (vaccinations)
Term
Miscellaneous Immune Thrombocytopenia Pathophysiology
Definition
cross reacting antibody causes thrombocytopenia
Term
Miscellaneous Immune Thrombocytopenia laboratory findings
Definition
platelet count not less than 50 x 10^9/L, resolves when infection is treated, reduced platelet count in fections, shortened platelet survvial, increased megakaryocytes in bone marrow and large platelets on peripheal blood smear
Term
Non-immune mechanisms of destruction etiology
Definition
DIC, TTP, HUS and artifical heart values
Term
Non-immune mechanisms of destruction pathophysiology
Definition
platelets are activated and consumes by aggregation within the circulation
Term
Non-immune mechanisms of destruction laboatory findings
Definition
low platelets
Term
Non-immune mechanisms of descreased production etiology
Definition
megakaryocyte hypolasia in bone marrow, ineffective thrombopoiesis, and hereditary or aquired conditions
Term
Non-immune mechanisms of decreased production pathophysiology
Definition
failure of bone marrow to deliver adequate platelets to the peripheral blood
Term
Non-immune mechanisms of decreased production laboatory findings
Definition
bone marrow function is abnormal, decreased platelet count
Term
Primary Thrombocytosis etiology
Definition
Chronic myeloproliferative disorders and myelodysplasia
Term
Primary Thrombocytosis pathophysiology
Definition
megakaryocyte proliferation and maturation bypass normal regulatory mechanisms
Term
Primary Thrombocytosis laboratory findings
Definition
platelet counts more than 1000 x 10^9/L
Term
seondary Thrombocytosis etiology
Definition
acute hemorrhage, surgery, post splenectomy, recovery form thrombocytopenia, malignantcy, chronic inflammatory diseases, IDA, and hemolytic anemia
Term
seondary Thrombocytosis pathophysiology
Definition
increased platelets caused by another disease or condition
Term
secondary Thrombocytosis laboratory findings
Definition
less than 1000 x 10^9/L platelet count but higher than normal
Term
Acute ITP clinical data
Definition
occurs in children, abrupt onset of bleeding, petechiae and superfical bleeding, infection common 1-3 weeks prior, no gender predilection, hemorrhagic bullar in mouth present in severe cases, duration in 2-6 weeks and sponteneous remissions occur in 93% of cases
Term
Acute ITP laboratory data
Definition
inital platelet count <20 x 10^9/L, eosinophilia and lymphocytosis are common
Term
Chronic ITP clinical data
Definition
occurs in adults, insidious onset of bleeding, petechiae and superfical bleeding, infection in unusual prior, gender predilection toward females (3:1), hemorrhagic bullar in mouth are usually absent, duration of mouths to years, and sponteneous remissions is rare, the course of the disease fluccuates
Term
Chronic ITP laboratory data
Definition
inital platelet count 30-80 x 10^9/L, eosinophilia and lymphocytosis are rare
Term
Pathophysiology of Thromocytopenia
Definition
could be due to increased destruction (immune mediated, drug mediated) or decreased production (acquired or inherited)
Term
Pathophysiology of thromocytosis
Definition
primary disease, secondary to another disease, or transient
Term
Bernard-Soulier Syndrome etiology
Definition
autosomal recessive trait, defect in platelet-vessel wall interactuon, disorder of adhesion
Term
Bernard-Soulier Syndrome pathophysiology
Definition
deficiency or defect in GP-Ib/IX/V
Term
Bernard-Soulier Syndrome clinical features
Definition
bleeding symptoms in homozygotes- pupura, epistaxis, gingival bleeding, menorrhaga without hemarthroses, deep visceral hematomas, can range from mild brusing to severe, recurrent mucocutaneous bleeding
Term
Bernard-Soulier Syndrome laboratory features
Definition
moderate to severe thrombocytopenia, large platelets with heterogenous size distribution on PBS, prolonged PT, absent platelet agglutination by ristocetin and vWF (not corrected by mixing studies), decreased GP-Ib/Ix/ and V by flow cytometrey
Term
Glantzmanns Thrombasthenia etiology
Definition
inherited qualitative platelet disorder in which there is defect in platelet-platelet interaction, autosomal recessive
Term
Glantzmanns Thrombasthenia pathophysiology
Definition
deficiency or defect in GPIIb/IIIa
Term
Glantzmanns Thrombasthenia clinical features
Definition
bleeding symptoms in homozygotes- purpura, epistaxis, gingival bleeding, mennorhagia, ranges from mild brusing to severe recurrent mucocutaneous bleeding beginnin at birth
Term
Glantzmanns Thrombasthenia labotaory features
Definition
normal platlet count and morphology, prolonged BT, absent platelet aggregationin response to ADP, collagen, thrombin and epinephrine, clot retraction, decreased GP-IIa/IIIa by flow cytometry, decreased platelet fibrinogen in alpha granules
Term
Delta storage pool disease etiology
Definition
inheretid qualitative platelet disorder in which there is defects of platelet secretion and signal transduction
Term
Delta storage pool disease pathophysiology
Definition
deficieny of platelet dense granules
Term
Delta storage pool disease clinical features
Definition
mild to moderate bleeding diathesis
Term
Delta storage pool disease laboratory features
Definition
prolonged BT, second wave of aggregation with ADP and EPI is absent and with collagen is decreased, ratio of ATP:ADP in increased
Term
Alpha storage pool disease etiology
Definition
inherited qualitative platlet defect, autosomal recessive
Term
Alpha storage pool disease pathophysiology
Definition
deficiencies in platelet alpha granules
Term
Alpha storage pool disease clinical features
Definition
lifelong bleeding diathesis
Term
Alpha storage pool disease laboratory features
Definition
gray platelets, mild thrombocytopenia with prolonged BT, platelet aggregation studies are normal
Term
defect in platlet agonist interaction etiology
Definition
hereditary defect
Term
defect in platelet agonist interaction pathophysiology
Definition
single agonist in platelet aggregation assays, abnormality is usually at the level of the platelet surface receptor for a specific agonist
Term
defect in platelet agonist interaction clincal features
Definition
bleeding
Term
defect in platelet agonist interaction laboratory features
Definition
normal platelet count, prlongs BT, normal platelet aggregation, abnormal second wave with ADP and collagen
Term
Biochemical mechanism for the effect of aspirin on platelet function
Definition
Aspirin impairs platelet aggregation by inhibition the acetylation of platelet cyclooxygenase.
Term
Recommended time frame for patients to refrain from taking aspirin before platelet function testing
Definition
7-10 days
Term
What platelet count indicates thrombocytopenia?
Definition
20.0 x 10 ^9/L
Term
What laboratory tests are most often ordered to screen for abnormalities of the hemostatic system?
Definition
Platlet count, PT, aPTT
Term
An average of 20 platelets pr field was counted on a blood smear from an EDTA specimen with a 1000x magnification. What is the platelet count estimate?
Definition
300 x 10^9/L
Term
What are purple lesions that are larger than 1 cm in diameter that are not raised called?
Definition
ecchymoses
Term
In which hematologic disorder would you expect to observe a decreased platelet count?
Definition
acute leukemia
Term
How long should a patient be off aspirin or aspirin-containing products before having platelet function testing?
Definition
7 days
Term
What can result in a falsely decreased platelet count on an automated hematology counter?
Definition
platelet satellitism
Term
what level of platelet count is associated with a risk of life-threatening bleed into the central nervous system?
Definition
5 x 10^9/L
Term
Thrombocytosis is
Definition
a platelet count above the reference range
Term
Platelet satillitism and platelet agglutination seen on a peripheral blood smear occur only
Definition
in blood collected in EDTA anticoagulant
Term
What disorder is probably indicated by a boy with petchiae on ankles, nosebleeds, recent infection?
Definition
ITP
Term
If a bone marrow examination had been performed on a child with suspected ITP, what morphology could it likley have shown?
Definition
normal to abnormal numbers of megakaryocytes
Term
What is the mechanism of platelet destruction in immuno thrombocytopenia
Definition
removal of antibody-coated platelets by splenic macrophages
Term
The small purple dots on a boys ankle are most probably?
Definition
petchiae
Term
What is the boy suspected of ITP, prognosis?
Definition
complete spontaneous recovery within 6 months
Term
What is characteristic in a patient with bernard souliers?
Definition
abnormal platelet aggregation with ristocetin
Term
What is found in Glanzmanns Thrombasthenia
Definition
genetic abnormality of GP IIb/IIIa
Term
Hereditary telangiestasia is characterized by
Definition
skin lesions that are arterioles connected directly to venules
Term
Platelet aggregation studies were performed and showed a primary wave of aggregation with ADP the returned to the baseline with no secondary wave, What is consistent with these results?
Definition
aspirin effect
Term
Reactve thrombocytosis is assciated with
Definition
post-surgery
Term
A patient who has small (less than 3 mm diameter) purple lesions on the extremities and a platelet count of 20 x 10^9/L probably has
Definition
petechiae
Term
Which platelet count is consistent with thrombocytosis?
Definition
2000 x 10^9/L
Term
A patient with a platelet count of 6 x 10^9/L might have which of the following symptoms?
Definition
petechiae, intracranial bleeding, and profuse bleeding from cuts in the skin
Term
Sites of bleeding in patients with thrombocytopenia are usually:
Definition
external skin and mucous membranes
Term
Chronic idiopathic thrombocytopenic purpura (ITP) is most common in
Definition
adult females between the ages of 20 and 40
Term
A screening test for primary hemostasis is
Definition
PT
Term
It is important to perform platelet counts on patients with thrombosis that are receiving heparin because
Definition
A significant number of patients will develop heparin-induced thrombocytopenia
Term
A patient with folic acid deficiency is likely to have
Definition
thrombocytopenia
Term
In which condition is a patient most likely to have a platelet count of 1500 x 10^9/L ?
Definition
essential thrombocythemia
Term
A patient with a severe nosebleed was seen in the emergency room of your hospital. When performing the evaluation of the peripheral blood smear, you noticed that at least 75% of the platelets were large- or giant-size. The platelets had abnormal morphology and appeared to have a large complement of granules. What condition may this patient have?
Definition
Bernard-Soulier syndrome
Term
Acute ITP is usually seen in
Definition
children 2 to 6 years old
Term
In which condition would a patient demonstrate a decreased platelet count because of ineffective thrombopoiesis?
Definition
megaloblastic anemia
Term
Which of the following is a characteristic laboratory finding in patients with Bernard-Soulier syndrome?
Definition
abnormal platelet aggregation response to ristocetin
Term
A patient with Bernard-Soulier syndrome will most probably have a mutation in the gene for:
Definition
glycoprotein Ib or IX
Term
A 25-year old female patient presented with a severe nosebleed and several spontaneous bruises but no other significant history. Laboratory tests showed a platelet count of 35 x 109/L. All other hematology parameters were within reference ranges. The most probable condition is:
Definition
chronic idiopathic thrombocytopenic purpura
Term
Which of the following is an acquired vascular disorder?
Definition
Henoch-Schoenlein purpura
Term
On questioning prior to drawing a blood sample for a platelet closure time and platelet aggregation studies, a patient told the clinical laboratory scientist that she had been taking three aspirin tablets a day for the past week for headaches. Which of the following is the correct action for the clinical laboratory scientist to take?
Definition
Inform the physician to request that the patient refrain from taking any more aspirin and return in 10 days for testing.
Term
Platelet adhesion is abnormal in patients with Bernard-Soulier syndrome because:
Definition
Glycoprotein Ib of the platelet membrane is defective.
Term
What is the mechanism of platelet destruction in patients with acute idiopathic thrombocytopenic purpura?
Definition
removal of antibody-coated platelets by splenic macrophages
Term
Daily platelet counts were performed on a patient who was started on heparin therapy. On the fifth day after therapy started, the platelet count suddenly dropped from the usual 300 x 109/L to 50 x 109/L. What is the most likely reason for the decrease in the platelet count?
Definition
heparin-induced thrombocytopenia
Term
Petechiae and several brusies on a patients arm causes which tests to be ordered?
Definition
platelet count, PT, and aPTT as screening tests.
Term
What results of these tests for a patient with petechiae and several brusies on arm would you expect (normal or abnormal) in this patient?
Definition
Petechiae indicated a platelet abnormality, the most common of which is thrombocytopenia. You would expect the platelet count to be decreased, the PT and aPTT would be normal in platelet abnormalities that are not complicated or accompanied by abnormalities of fibrin formation
Term
Patient has an average of 14 platelets per high power field on a peripheal blood smear prepared from a needle tip and your laboratory allowed correltation between the direct intrument count and the blood smear estimate of 20%, what range would you expect the instrument to be?
Definition
14 x 15 x 10^9/L = 210 x 10^9/L
Term
Is a platelet count of an average of 14 platelets per high power field on a peripheal blood smear within an acceptable reference range?
Definition
An acceptable range of the instrument count would be 168-252 x 10^9/L, which is within acceptable reference range
Term
How many platelets per 1000 x field would you expect to observe on the peripheral blood smear of a patient with acute ITP?
Definition
You would expect to see an aveage of fewer than 6 platelets per field. It can be difficult to find platelets on the blood smear of patients with ITP
Term
a 6 year old boy comes into his doctor because his mother noticed small pink spots on his legs, several bruises on his arms and legs, platelet count was 20 x 10^9/L, PT and aPTT were within normal limits. The CBC was normal escept for the low platelets. No previous history of bleeding but he got the spots after the hepatitis vaccine. What is the most probable type of thrombocytopenia? Should other coagulation tests be performed at this time?
Definition
The most probable type of thrombocytopenia experienced by this patient is an immune type of increased destruction, which is reportedly associated with viral infections in some children. Other coagulation tests are not neccesary
Term
What is the pathophysiology of thrombocytopenia in megaloblastic anemia?
Definition
Thrombocytopenia occurs in megaloblastic anemia because of ineffective production of all myeloid cell lines in the bone marrow
Term
Why is primary thrombocytosis associated with abnormal platelet function while secondary thromcytosis is not?
Definition
Primary thrombocytosis is associated with the myeloproliferative disorders, which are clonal disorders of the pluripotent stem cell. The abnormal clone grows autonomously and not in resposne to normal regualtory factors. It is likley that abnormalities in platelet function are aquired along with the ability to grow autonomously. In secondary thrombocytosis the platelets are increased because the normal regualtory routes in response to a need for more platelets
Term
platelet aggregation studies in plateelet adhesion disorders
Definition
Platelet adhesion to collagen requires that the vWF attached to platelet GPIb/IX receptros bridge the platelet to the collagen fiber. Aggregation studies are abnormal with ristocetin because it takes the place of collagen in the test.
Term
Why are the bleeding time test and closure time abnormal for up to 7 days flollowing ingestion of aspirin?
Definition
Aspirin inhibits the platelet enzyme cyclooxygenase, which is neccesary for production of thromboxane A2. TXA2 is necesary in the activated platelet for secretion of granule contents and therefore the function of the platelets is impaired. The defective platelets continue to circulate for their normal life spin (10 days), because they are ciculating the bone marrow is not overstimulated to produce new platelets to replace defective ones
Term
platelet aggregation studies in aggregation disorders
Definition
involved abnormalities in the GPIIb/IIIa receptor or in fibrinogen. Other routine agonists require GPIIb/IIIa receptor and fibrinogen as the bridge to attach one platelet to another platele. Platelet aggregation studies will be abnormal with all agonists except ristocetin
Term
platelet aggregation studies in secretion disorders
Definition
platelets are able to respond to agonists in the primary wave of aggregation but are unable to release their own ADP and manufacture their own Thromboxane A2, so that the secondary wave of aggregation seen with ADP and epinephrine and wave of aggregation with collagen are abnormal
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