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Hematology and Oncology > EXAM #1: THROMBOCYTOPENIA > Flashcards

EXAM #1: THROMBOCYTOPENIA Flashcards

1
Q

What is the definition of thrombocytopenia?

A

Platelet count less than 150,000/microliter

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2
Q

Describe the appearance of platelets on PBS.

A
  • Round- oval
  • Blue-gray
  • 1/3 the size of a RBC
  • Anuclear
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3
Q

Where are platelets produced? What are they released from?

A
  • Produced in the bone marrow

- Megakaryocytes

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4
Q

What regulates platelet production? Where is this factor synthesized?

A

Thrombopoietin, which is synthesized in the liver

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5
Q

What receptor is activated after binding of Gp1b to vFW?

A

GpIIb/IIIa, which binds fibrin

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6
Q

What are the three underlying causes of thrombocytopenia?

A

1) Underproduction
2) Destruction
3) Sequestration

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7
Q

What are some of the infectious causes of platelet underproduction?

A

1) HIV

2) Parvovirus B19

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8
Q

What is the most common cause of underproduction of platelets from the bone marrow?

A
  • Chemotheraputic agents

- Alcohol

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9
Q

If the MCV is greater than 115 or more, what should you think?

A

Megaloblastic anemia i.e. B12 or Folate

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10
Q

What is the mechanism of thrombocytopenia in pernicious anemia?

A

B12 is necessary to DNA synthesis, i.e. synthesis of platelet precursors

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11
Q

What will the megakaryocyte levels be in pernicious anemia?

A

Normal to increased numbers for megakaryocytes

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12
Q

What cancer is associated with pernicious anemia?

A

Gastric carcinoma

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13
Q

How is pernicious anemia managed?

A

B12 supplementation

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14
Q

What is pseudothrombocytopenia?

A

Platelet aggregation or clumping in vitro leads to a low count

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15
Q

What triggers pseudothrombocytopenia? How do you correct for it?

A
  • EDTA

- Recheck with citrated or heparanized blood tube i.e. purple tube

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16
Q

What is ITP?

A

Idiopathic or Immune Thrombocytopenic Purpura

17
Q

Describe the pathology of ITP.

A
  • Accelerated destruction of platelets b/c antibody coated platelets are destroyed by macrophages in spleen
  • GpIIb/IIIa
  • Normal or increased megakaryocytes
  • Diagnosis of exclusion*
18
Q

What is the typical clinical presentation of ITP?

A

Often asymptomatic with SEVERE thrombocytopenia

Some have purpura, petechiae…etc. but LIFE-THREATENING bleeding is RARE

19
Q

What is the treatment for ITP?

A
  • Observation
  • Steroids
  • IVIG–coat receptors with something other than antiplatelet antibody
  • Rituximab
  • Thrombopoetin
  • Splenectomy
20
Q

What are the two classes of platelet destruction?

A
  • Immune-mediated

- Nonimmune-mediated

21
Q

List the causes of immune-mediated platelet destruction.

A
  • ITP
  • HIT
  • Post transfusion purpura
  • Medications
  • Antiphospholipid antibody syndrome
22
Q

List the causes of nonimmune-mediated platelet destruction.

A
  • DIC
  • TTP/HUS
  • HELLP Syndrome
  • Gestational Thrombocytopenia
  • Mechanical Destruction
  • Localized intravascular coagulopathy
23
Q

What is HIT?

A

Heparin Induced Thrombocytopenia

  • Immune mediated destruction of platelets
  • Antibodies to heparin AND platelet-specific PF4 complex
  • Activates platelets and leads to thrombosis
24
Q

What form of Heparin has a lower risk of HIT associated?

A

LMWH

25
Q

How is HIT managed?

A

1) STOP heparin

2) Use alternative anti-coagulant

26
Q

Can you use Heparin again in a patient that has developed HIT?

A

Yes, if they have been Heparin free for 6 months

27
Q

What does jaundice not involving the sclera indicate?

A

NOT hyperbilirubinemia

28
Q

What causes sequestration of platelets?

A

Splenomegaly leads to splenic sequestration

  • Portal HNT
  • Hereditary spherocytosis
  • CML
  • Hairy cell leukemia
  • MALT lymphoma
29
Q

How do you evaluate thrombocytopenia?

A

1) HIP and PE
2) Lab eval
3) Bone marrow biopsy

30
Q

When is bone marrow indicated?

A

1) Multiple cell lines involved
2) Greater than 60 with isolated thrombocytopenia
3) When empiric therapy is unsuccessful

31
Q

What is the formula for platelet transfusion?

A

1 unit= increase in 5,000

Normal 6-pack is 30,000

32
Q

When is platelet transfusion a BAD idea?

A

ITP

HIT

Hematology and Oncology (38 decks)

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