Lecture 8: Platelet Disorders Flashcards

1
Q

ITP may be part of a broader disease affecting immune regulation such as what?

A
  • HIV infection
  • SLE
  • Lymphoproliferative malignancy, especially in older pt’s
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2
Q

All pt’s with ITP should be screened for what infection; recent research has also linked ITP to what other infective agent?

A
  • All pt’s should be screened for HIV
  • Recent reports have linked ITP to H. pylori infection
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3
Q

What will blood smear of someone with ITP show?

A

Decreased platelets and occasional large platelets (megathrombocytes)

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4
Q

ITP can be triggered by almost any drug, but is most commonly seen in association with what?

A

Quinine or Quinidine

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5
Q

What are 2 effective therapies for ITP with severe thrombocytopenia or active bleeding is present?

A

Glucocorticoids and IVIG

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6
Q

Which 2nd line immunosuppressive agent will lead to doubling of the platelet count in 40% of pt’s with ITP?

A

Rituximab

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7
Q

Is splenectomy indicated for ITP?

A

Rarely, only in those w/ significant bleeding unresponsive to immunosuppressive medications

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8
Q

What should a CBC of pt with ITP show in terms of platelets, Hgb, Hct, and leukocytes?

A
  • Low platelet count
  • Normal Hgb, Hct, and leukocyte count
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9
Q

Although pt’s with heparin induced thrombocytopnia do not bleed excessively they have a dramatic risk what complications?

A
  • DVT’sandPE’s
  • Unusual clotting problems i.e., portal vein thrombosis or acute arterial occlusion
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10
Q

Which type of heparin is more likely to lead to HIT and which is less likely?

A
  • Unfractionated heparin = more likely
  • Incidence is 2-3x lower in pt’s receiving LMW heparin
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11
Q

What is the “4T Score” used clinically to determine the likelihood of HIT?

A
  • Degree of Thrombocytopenia
  • Timing of platelet count fall
  • Thrombosis or other sequelae
  • Other causes for Thrombocytopenia present
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12
Q

Describe the degree of thrombocytopenia associated with 2, 1, or 0 points using the “4T Score” in assessing HIT risk?

A
  • 2 points = platelet count >50% fall and nadir ≥20,000/uL
  • 1 point = platelet count 30-50% fall or nadir 10,000-19,000/uL
  • 0 points = platelet count <30% fall or nadir <10,000/uL
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13
Q

Describe the timing of platelet count fall associated with 2, 1, or 0 points using the “4T Score” in assessing HIT risk?

A
  • 2 points: clear onset btw days 5 and 10 or platelet count decrease at ≤1 day if prior heparin exposure within last 30 days
  • 1 point: onset after day 10 or timing unclear, or ≤ day 1 if heparin exposure within past 30-100 days
  • 0 points: platelet count fall <4 days without recent exposure
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14
Q

Describe the thrombosis or other sequelae category associated with 2, 1, or 0 points using the “4T Score” in assessing HIT risk?

A
  • 2 points: confirmed nw thrombosis, skin necrosis, or acute systemic rxn after IV unfractionated heparin bolus
  • 1 point: progressive or recurrent thrombosis, nonnecrotizing (erythematous) skin lesions, or suspected thrombosis not proven
  • 0 points: no thrombosis or sequelae
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15
Q

Which findings for the category “other causes of thrombosis” are associated with 2, 1, or 0 points using the “4T Score” in assessing HIT risk?

A
  • 2 points = no other cause apparent
  • 1 point = another cause is possible
  • 0 points = definite other cause
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16
Q

How many points using the “4T Score” for risk of HIT is associated with low, intermediate, and high probability of HIT?

A
  • Low = 0-3 points
  • Intermediate = 4-5 points
  • High = 6-8 points
17
Q

In patients with HIT, heparin should be discontinued and what should be administered?

A

Direct thrombin inhibitors (i.e., Lepirudin or argatroban)

18
Q

Which findings is the simplest way to differentiate TTP from HUS?

A
  • TTP = MAHA + thrombocytopenia (<50,000) + fever + neurologic sx’s
  • HUS = add renal failure to the above
19
Q

How do the hereditary vs. acquired forms of TTP differ?

A
  • Hereditary = mutation of ADAMTS13 gene
  • Acquired = autoantibodies directed at ADAMTS13; linked to pregnancy, HIV-infection, chemotherapy and immunosuppressive agents
20
Q

What is the treatment for TTP?

A
  • As in DIC, treat the underlying cause
  • Plasmapheresis - life saving in virtually 100% of cases
  • Glucocorticoids also recommended
21
Q

How should young patients with TTP-HUS with features suggesting enteric bacterial toxins as the etiology be treated?

A

Supportively

22
Q

What is the pathologic lesion of TTP; what will be seen on peripheral smear?

A
  • Pathologic lesion is hyaline microthrombi which occlude the capillaries of virtually every organ in the body
  • Schistocytes seen on peripheral smear
23
Q

What is the hallmark of essential thrombocythemia and how is the diagnosis made?

A
  • Thrombocytosis that cannot be explained by clinical conditions known to cause a reactive elevation in platelet count
  • Dx made by finding persistent platelet counts >600,000 u/L with no other condition present leadin to reactive thrombocytosis
24
Q

What are some genetic findings which can be helpful in diagnosing essential thrombocythemia?

A
  • 50% of pt’s will have JAK2 mutation
  • Since thrombocytosis may be seen in CML and PRV, diagnosis further requires that the Philidelphia chromososme be negative and the pt does not have concomitant erythrocytosis
25
Q

What are 3 criteria which would place a patient with essential thrombocythemia in a low-risk category; how should they be treated?

A
  • Those aged <60 year, have no prior thromboembolic event and platelet counts <1,000,000/uLhaveexcellent prognosis
  • Should be observed without treatment
26
Q

Pt’s with essential thrombocythemia who are not in the low-risk category should be treated how?

A

Tx with hydroxyurea + low-dose aspirin

27
Q

Which 2 drugs can be added to reduce platelet count in pt with ET if deemed necessary based on sx’s refractory to salicylates alone?

A

Pegylated IFN-α or Anagrelide

28
Q

Reactive thrombocytosis is almost always due to what 4 etiologies?

A
  • Iron deficiency
  • Inflammation
  • Cancer
  • Infections