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Heme/Lymph Exam > Pathology of Hemostasis Disorders > Flashcards

Pathology of Hemostasis Disorders Flashcards

1
Q

thrombocytopenia - defined

A

*defined by platelets < 150,000
*spontaneous bleeding occurs at platelets < 20,000
-usually involves small vessels of skin, mucous membranes, GI/GU tracts
-intracranial bleeding can be serious!

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2
Q

causes of thrombocytopenia

A
  1. decreased platelet production = bone marrow problems (aplastic anemia, MDS, vitamin deficiency, tumors)
  2. decreased platelet survival
    a. immunologic (circulating anti-platelet antibodies to GpIIb/IIIa or GpIB) - ex. ITP, HIV, drugs
    b. mechanical destruction/consumption - ex. MAHA, prosthetic heart valves
  3. sequestration
  4. dilutional
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3
Q

thrombocytosis - defined

A

*defined by platelets > 350K
*complications:
-thrombotic episodes, due to increased number of active platelets
-bleeding episodes, as platelet function may also be defective

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4
Q

causes of thrombocytosis

A
  1. primary causes: myeloproliferative neoplasms (essential thrombocytosis, CML, PV, PMF)
  2. secondary/reactive causes: infections, iron deficiency, inflammatory disorders, etc
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5
Q

immune thrombocytopenic purpura (ITP) - pathogenesis

A

*antiplatelet antibodies to GpIIb/IIIa or GpI/IX:
-coat platelets, which are selectively removed from circulation by the spleen

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6
Q

immune thrombocytopenic purpura (ITP) - causes

A

*may be secondary or primary (idiopathic)
1. acute:
-children
-self-limiting
-post acute viral infection

  1. chronic:
    -adults
    -autoimmune syndromes, infections, drugs, HIV
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7
Q

immune thrombocytopenic purpura (ITP) - diagnosis

A

*isolated thrombocytopenia in otherwise healthy pt (no other cell counts low)
*NORMAL PT, aPTT
*normal/increased numbers of megakaryocytes in bone marrow

*RULE OUT: no known exposure to thrombocytopenic agents

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8
Q

ddx for: increased PT, normal aPTT, normal platelets

A

*VII, X, V deficiencies
*Vitamin K deficiency

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8
Q

ddx for: normal PT, elevated aPTT, normal platelets

A

*VIII, IX, XI deficiencies
*VWD
*heparin

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9
Q

ddx for: elevated PT, elevated aPTT, normal platelets

A

liver disease

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10
Q

ddx for: elevated PT, elevated aPTT, decreased platelets

A

DIC

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11
Q

ddx for: normal PT, normal aPTT, decreased platelets

A

*hypersplenism
*platelet destruction/production (ITP, TTP, HUS)

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12
Q

ddx for: normal PT, normal aPTT, increased platelets

A

reactive vs. myeloproliferative disorder

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13
Q

D-dimer lab test

A

*specific plasmin-mediated breakdown product of cross-linked fibrin
*normal < 200 ng/mL
*useful for:
-DIC (level usually very elevated)
-DVT, post-op, acutely ill level elevated, not as high as seen in DIC

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14
Q

RBC fragmentation syndromes

A
  1. mechanical/vascular hemolysis: direct mechanical trauma from hemodynamic defect or extreme turbulence
    -prosthetic heart valves, vascular malformations, malignant hypertension, severe burns, “March hemoglobinuria”
  2. microangiopathic hemolytic anemias (MAHA): endothelial damage in microvasculature
    -DIC, TTP, HUS
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15
Q

microangiopathic hemolytic anemias (MAHA)

A

*RBCs are damaged when passing through obstructed or narrowed vessels
*causes intravascular hemolysis
*examples:
1. disseminated intravascular coagulation (DIC)
2. thrombotic thrombocytopenic purpura (TTP)
3. hemolytic uremic syndrome (HUS)

16
Q

disseminated intravascular coagulation (DIC) - overview

A

*a secondary condition in which microthrombi develop throughout the bloodstream, blocking small blood vessels and depleting platelets and clotting factors needed to control bleeding

17
Q

disseminated intravascular coagulation (DIC) - pathogenesis

A

*simultaneous systemic activation of:

  1. coagulation system:
    -widespread expression of tissue factor (TF)
    ~intravascular thrombus formation (compromising blood supply to various organs)
    ~exhaustion of platelets and coagulation factors, resulting in hemorrhage
  2. fibrinolytic system:
    -plasmin degrades fibrinogen and fibrin, producing fibrin degradation products, exacerbating bleeding
18
Q

disorders associated with disseminated intravascular coagulation (DIC)

A

*malignancies (solid tumor, hematologic)
*obstetric emergencies (amniotic fluid embolism, abruptio placentae)
*organ destruction (severe pancreatitis, severe hepatic failure)
*sepsis/severe infection
*severe toxic or immunologic reactions
*trauma
*vascular abnormalities

19
Q

disseminated intravascular coagulation (DIC) - common triggers

A
  1. massive tissue destruction
  2. sepsis
  3. endothelial cell injury

note - all three of these cause mass release of tissue factor

20
Q

disseminated intravascular coagulation (DIC) - clinical features

A

*usually severe bleeding:
-petechiae/ecchymoses of skin/mucous membranes
-shock
*signs of the underlying disease are usually present
*organ(s) involved with accompanying clinical signs must also be taken into consideration

21
Q

disseminated intravascular coagulation (DIC) - LABS

A

*increased PT
*increased aPTT
*decreased platelets (thrombocytopenia)
*increased D-dimers
*microangiopathic hemolytic anemia with SCHISTOCYTES on peripheral smear

22
Q

thrombotic thrombocytopenic purpura (TTP) - clinical pentad

A

*microangiopathic hemolytic anemia (decreased Hb, schistocytes, and increased LDH)
neurologic abnormalities**
**renal insufficiency (decreased creatinine)
*fever
*thrombocytopenia

23
Q

thrombotic thrombocytopenic purpura (TTP) - pathophysiology

A

inhibition or deficiency of ADAMTS13 (a vWF metalloprotease) -> decreased degradation of vWF multimers -> increased large vWF multimers -> increased platelet adhesion and aggregation (microthrombi formation)

24
Q

thrombotic thrombocytopenic purpura (TTP) - lab diagnosis

A

*deficiency of vWF metalloprotease ADAMTS13 (results in accumulation of very-high-molecular-weight multimers of vWF, promoting platelet aggregation)
*consumptive thrombocytopenia (LOW PLATELETS)
*NORMAL PT and PTT
*MAHA with schistocytes in blood smears (low Hb, high LDH)

25
Q

hemolytic uremic syndrome (HUS) - clinical features

A

*microangiopathic hemolytic anemia (decreased Hb, schistocytes, increased LDH)
*thrombocytopenia
*renal insufficiency
*bloody diarrhea

26
Q

hemolytic uremic syndrome (HUS) - pathogenesis

A

*predominantly caused by Shiga toxin-producing E. coli (STEC) infection (serotype 0157:H7), which causes profound endothelial dysfunction

27
Q

hemolytic uremic syndrome (HUS) - lab diagnosis

A

*E. coli 0157:H7 infectious gastroenteritis:
-elaborates shiga-like toxin absorbed by GI tract and binds to endothelial cells, initiating platelet activation
*consumptive thrombocytopenia
*NORMAL PT and PTT
*MAHA with schistocytes in blood smears (low Hb, high LDH)

28
Q

what can help you distinguish TTP from HUS?

A
  1. HUS = bloody diarrhea; TTP = neuro symptoms
  2. HUS = E. coli 0157:H7; TTP = ADAMTS13 deficiency
29
Q

von Willebrand Factor (vWF) - functions

A
  1. binds to GpIb receptor on platelets adhesion to damaged epithelium
  2. carrier protein for VIII (stabilized VIII, increasing serum half life)
30
Q

von Willebrand Disease (VWD) - epidemiology

A

*most common bleeding disorder
*affects 1% of general population
*autosomal dominant OR recessive:
-multiple genetic mutations
-results in either a QUANTITATIVE or QUALITATIVE deficiency of vWF

31
Q

von Willebrand Disease (VWD) - diagnostic approach

A

*hematologic evaluation of peripheral blood
*screening for hemostasis (platelet count, PT, aPTT, etc)
*VWD panel (esoteric testing):
-decreased factor VIII activity
-decreased vWF antigen
-decreased ristocetin cofactor activity

32
Q

Factor VIII deficiency (Hemophilia A) - labs

A

*prolonged PTT, normal PT
*factor VIII-specific assays are required

33
Q

acquired coagulopathies

A
  1. liver disease:
    -liver is the major site of clotting factor synthesis
    -hepatitis/cirrhosis
    -results in bleeding diathesis
  2. Vitamin K deficiency
    -biliary obstruction, malabsorption syndromes, nutritional deficiencies
    -drugs affecting gut flora
    -results in bleeding diathesis
  3. DIC
    -tissue factor express
    -results in purpuric manifestations
34
Q

Factor V Leiden - epidemiology

A

*most common inherited thrombotic disorder
*accounts for 20-50% of thrombotic disorders
*autosomal dominant:
-point substitution resulting in Arg506 -> Gln
-mutation in Factor V renders it resistant to proteolysis by activated Protein C

35
Q

Factor V Leiden - clinical features

A

*recurrent venous thromboembolism, may be asymptomatic

36
Q

Factor V Leiden - diagnosis

A

DNA mutational analysis

37
Q

Factor V Leiden - treatment

A

*prophylactic anticoagulation (warfarin)

Heme/Lymph Exam (38 decks)

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