Disorders Affecting Platelets and Coag Flashcards
Thrombotic Thrombocytopenic Purpura (TTP)
- Etiology: Caused by spontaneous aggregation of platelets and activation of the coagulation in the small blood
vessels. Platelets are consumed in the aggregation process, and bind vWF. These platelet-vWF complexes form
small blood clots which circulate in the blood vessels and cause shearing of red blood cells, resulting in their
rupture. - Laboratory Diagnosis:
o Decreased hemoglobin
o Marked decrease in platelets
o Polychromasia
o Microspherocytes, schistocytes, keratocytes
o nRBCs may be presen
Hemolytic Disease of the Newborn (HDN)
- Platelets may be destroyed as a result of their interaction with products of RBC breakdown, rather than their
direct participation in an immunologic reaction
Hemolytic Uremic Syndrome (HUS)
- Etiology: Resembles TTP except it is found in children 6 months to 4 years of age and is self-limiting. Mostly
caused by Shigella dysenteriae or Escherichia coli O157. Toxins enter the bloodstream and attach to renal
glomerular capillary endothelial cells which become damaged and swollen leading to formation of hyaline
thrombi. This results in development of renal failure, thrombocytopenia, and microangiopathic hemolytic
anemia. Adult form of HUS is seen with exposure to immunosuppressive agents or chemotherapeutic agents. - Laboratory Diagnosis:
o Thrombocytopenia
o Renal failure: increased blood urea nitrogen and creatinine
o Urine shows RBCs, protein and casts
o Decreased hemoglobin
o Elevated reticulocyte count
o Schistocytes
Disseminated Intravascular Coagulation (DIC)
- Etiology: Activation of the coagulation cascade resulting in a consumptive coagulopathy that entraps platelets
in intravascular fibrin clots. Similar to TTP except thrombi are composed of platelet and fibrinogen; whereas,
TTP thrombi are composed of platelet and vWF. - Laboratory Diagnosis:
o Elevated D-Dimer
o Decreased Fibrinogen
o Thrombocytopenia
o Clinical presentation
Acute Idiopathic Thrombocytopenic Purpura (AITP)
Etiology: Immunologically mediated arising without apparent cause or underlying disease state. Primarily a
disorder of children. Characterized by the onset of bruising, petechiae, and sometimes epistaxis.
* Laboratory Diagnosis:
o Thrombocytopenia
o May occur after Rubella, chickenpox, or other viral illnesses
o Normal CBC
o Recent onset of bleeding signs and symptoms with no family history of hemorrhagic abnormalities
Chronic Idiopathic Thrombocytopenic Purpura (CITP)
- Etiology: Immunologically mediated arising without apparent cause or underlying disease state. Can be found
in patients of any age but primarily 20 to 50. - Laboratory Diagnosis:
o Decreased platelets but can vary from decreased and near normal over periods of time
o May have increased MPV
o Bone marrow shows megakaryocytic hyperplasia
Heparin-Induced Thrombocytopenia (HIT)
- Etiology: adverse effect of treatment with unfractionated heparin. Some patients develop an IgG antibody to
heparin-platelet factor 4 immune complexes. In other patients the immune complexes that are formed bind
platelet Fc receptors, which leads to platelet activation, thrombocytopenia, and formation of microvascular
thrombi. - Laboratory Diagnosis:
o Decreased platelet count while receiving heparin therapy
Bernard-Soulier Syndrome
- Etiology: rare syndrome usually manifested in infancy or childhood with hemorrhage characteristic of
defective platelet function. GPIb/IX/V is missing from platelet surface or exhibits abnormal function. Lack of
GPIb/IX/V results in lack of binding to vWF, which accounts for the inability of platelets to adhere to exposed
subendothelium. - Laboratory Diagnosis:
o Giant platelets
Glanzmann Thrombasthenia
- Etiology: Abnormal in vitro clot retraction and a normal platelet count. This is due to deficiency or abnormality
of GPIIb/IIIa, a membrane receptor capable of binding fibrinogen, vWF, fibronectin and other adhesive ligands. - Laboratory Diagnosis:
o Markedly prolonged bleeding time
o Normal platelet count and morphology
o Ristocetin-induced binding of vWF to platelets is normal
o CBC is normal unless underlying disorder
Gray Platelet Syndrome
- Etiology: The alpha-granules are the storage site for proteins produced by the megakaryocyte or present in
plasma and taken up by platelets and transported to alphagranules for storage. Gray platelet syndrome is characterized
by the specific absence of morphologically recognizable alphagranules in platelets. - Laboratory Diagnosis:
o Prolonged bleeding time
o Lifelong mild bleeding tendencies
o Moderate thrombocytopenia
o Large platelets with gray appearance
Uremia
- Etiology: guanidinosuccinic acid (GSA) is present in circulation
in higher than normal amounts as a result of inhibition of the urea cycle resulting in abnormal platelet
function. - Laboratory Diagnosis:
o Prolonged bleeding times and correlates with severity of renal failure
o Decreased hematocrit
Liver Disease
Laboratory Diagnosis:
o Decreased clotting proteins
o Dysfibrinogenemia and excessive fibrinolysis
o Mild to moderate thrombocytopenia
o Prolonged bleeding times
Hemophilia A
Factor VIII Deficiency
Varies from asymptomatic to crippling bleeding/hemorrhage
PLT:N PT:N APTT: increase Factor 8: Decrease
Hemophilia B (Christmas Disease )
Factor IX Deficiency
Varies from asymptomatic to crippling bleeding/hemorrhage
PLT:N PT:N APTT: increase Factor 9:Decrease
Factor XIII Deficiency
Factor XIII Deficiency
Poor Wound Healing and keloid Formation
PT:N APTT:N
Von Willebrand Disease
Deficiency in VWF. Platelets can’t adhere to collagen to form plt plug. MOST COMMON BLEEDING DISORDER
Lab: PLT:N Closure time (PFA): N or inc
PT: N APTT: N or inc
Factor VIII: N or Inc VWF Antigen: decrease
Primary Thrombocytosis
Unregulated production of megakaryocytes in bone marrow . Ex myeloproliferative neoplasm with essential thrombocythemia leading to thrombosis or hemorrhage. Lab: PLT >600 *10E9, giant platelet, platelet aggregation
Secondary or reactive thrombocytosis
increase PLT due to another condition , ex hemorrhage, surgery, splenectomy and IDA
LAB: Lab >450 but less than 1000
Thrombocytopenia
- Decreased production (aplastic anemic, MDS, chemotherapy, severe vial infection
- Increase destruction (immune thrombocytopenic purapura, drugs, DIC, etc)
PLT lower than 150
