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HemOnc Week 2 > LM 6.3: Disorders of Hemostasis > Flashcards

LM 6.3: Disorders of Hemostasis Flashcards

1
Q

what platelet count classifies as thrombocytopenia?

A

<100,000 platelets/mL

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2
Q

what platelet count classifies as thrombocytosis?

A

> 600,000 platelets/mL

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3
Q

what is thrombocytopathy?

A

disorders of platelets function

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4
Q

what do you usually see in the history of someone with a platelet disorder?

A
  1. mucocutaneous bleeding
  2. heavy menses
  3. alcohol
  4. family history of bleeding
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5
Q

what do you see during the physical exam of someone with a platelet disorder?

A
  • petechia
  • purpura
  • enlarged spleen
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6
Q

what are the categories of disorders of platelet function?

A
  1. congenital
  2. acquired
    - due to drug exposure
    - due to systemic disease
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7
Q

what tests do you do for platelet function disorders?

A

platelet count would be normal!!

but the platelet function screening tests would be abnormal

  1. platelet aggregation study
  2. platelet electron microscopy
  3. thomboelastography
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8
Q

what are the types of congenital platelet storage pool disorders?

A
  1. deficiency of the storage granules of the platelets

2. malfunction of the granule secretory mechanism (aspirin-like defect)

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9
Q

which diseases are congenital platelet receptor disorders?

A
  1. Glanzmann’s thrombasthenia

2. Bernard Soulier syndrome

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10
Q

what is Glanzmann’s thrombasthenia?

A

deficiency of the IIb/IIIa receptors on the platelet membrane

this is the receptor for fibrinogen

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11
Q

what is Bernard Soulier syndrome?

A

deficiency of the Ib receptor

this is the receptor for von willebrand factor

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12
Q

which medications can cause acquired disorders of platelet function?

A
  1. non steroidal anti-inflammatory drugs all reduce platelet function

the effect of aspirin is irreversible so 7-10 days are required for an entirely new population of normally functioning platelets to be present –> 7-10 days is the lifespan of a platelet

  1. Clopidogrel (Plavix) and other anti-platelet drugs are also irreversible
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13
Q

which systemic disorders can cause acquired disorders of platelet function?

A
  1. uremia
  2. cardiopulmonary bypass
  3. paraproteinemia
  4. disseminated intravascular coagulation (DIC)
  5. myeloproliferative and myelodysplastic disorders

treatment of these underlying disorders is the best way to correct the platelet dysfunction

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14
Q

why can uremia cause acquired disorders of platelet function?

A

uremia = severe kidney dysfunction

there can be an increased risk of bleeding due to an accumulation of toxic metabolites

best therapy is hemodialysis

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15
Q

what is pseudo thrombocytopenia?

A

aka EDTA induced thrombocytopenia

a disorder due to autoantibodies int he patient that cause the patient’s platelets to clump in the test tube used for the CBC (EDTA is the anticoagulant in the tube!)

this causes an artificially low platelet count even though the real platelet count in the patient is fine

you would need to get another sample of blood but use heparin in the tube instead of EDTA to confirm that the platelet count is really normal

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16
Q

what are the various mechanisms of thrombocytopenia?

A
  1. decreased production of platelets in the bone marrow - like from toxic drugs
  2. dilution of platelets in the peripheral blood - like from a transfusion of platelet-poor blood
  3. maldistribution of platelets - like in patient with large spleens
  4. excessive consumption/destruction of platelets in circulation - like in autoimmune thrombocytopenia
17
Q

what are the clinical clues that suggest thrombocytopenia due to reduced platelet production?

A
  • normal sized platelets on blood smear
  • anemia or abnormal WBCs might be seen on blood smear
  • significant bleeding in patient
18
Q

what could cause thrombocytopenia due to reduced platelet production?

A
  • chemo
  • alcohol
  • drugs
  • HIV
  • HepC
  • parvovirus

these all suppress platelet production

19
Q

when should you avoid a platelet transfusion?

A

if there’s splenomegaly

infusing with platelets won’t help because they’ll all just pool in the large spleen

20
Q

what clinical clues would suggest thrombocytopenia due to increased consumption/destruction of platelets?

A
  • large platelets on the blood smear

- bleeding is often less than expected considering the platelet count

21
Q

what are some disorders that are associated with thrombocytopenia due to increased consumption/destruction of platelets?

A
  • autoimmune disorders like immune thrombocytopenia purpura (ITP)
  • viral infections, especially in kids
  • HIV positive patients
  • heparin induced thrombocytopenia
22
Q

what is adult ITP?

A

Immune thrombocytopenic purpura

  • more common in women
  • mucocutaneous bleeding
  • NO splenomegaly
  • platelets are coated with antibodies
23
Q

what is the treatment for adult ITP?

A
  1. corticosteroids
  2. high dose immunoglobulin
  3. rituxan
  4. splenectomy

initial therapy should be steroids - only use high dose immunoglobulin if there is severe thrombocytopenia or life-threatening bleeding

second line defense is Rituxan if steroids don’t increase platelet count

24
Q

what is childhood ITP?

A

usually happen after a viral illness

the antibody is usually against a viral protein antigen and the platelets become sensitized by the viral antigen absorbed on the platelet membrane or by the viral/antibody complexes on the platelet membrane

usually self limiting and resolves by itself in 2-3 months

avoid splenectomy

25
Q

what is acquired TTP?

A

thrombotic thrombocytopenic purpura

potentially fatal

acute onset

thought to be due to antibodies against the von willebrand cleaving protease leading to large von willebrand multimers in the blood which induce spontaneous platelet aggregation

**inhereted TTP is non-immune

26
Q

what are the lab test results you get for acquired TTP?

A

severe thrombocytopenia

microangiopathic hemolytic anemia

elevated LDH

27
Q

what are the clinical features of acquired TTP?

A

fever

fluctuating neurological status

renal insufficiency

28
Q

what conditions can lead to acquired TTP?

A
  • acute viral or bacterial illness
  • pregnancy
  • oral contraceptives
29
Q

what is HUS?

A

hemolytic uremic syndrome

it’s a non-immune destructive thrombocytopenia

mainly in children

may be preceded by a viral or bacterial illness

patients usually have bloody diarrhea due to e. coli or shigella dysenteriae –> both of these organisms realize toxins that damage the renal capillary endothelium

30
Q

what is the best therapy for TTP and HUS?

A

plasmapheresis/plasma exchange

try to avoid platelet transfusion if possible

31
Q

which diseases are non-immune destructive thrombocytopenia?

A

TTP

HUS

32
Q

what is primary/essential thrombocytosis?

A

a clonal defect of the hematopoietic stem

it’s a malignany disorder and is considered a part of the myeloproliferative syndromes

33
Q

what is reactive thrombocytosis?

A

an elevated platelet count (> 450,000/mcL) that develops secondary to another disorder

34
Q

what are some of the causes of reactive thrombocytosis?

A
  • post-splenectomy state
  • iron deficiency
  • acute hemorrhage
  • chronic inflammation
  • malignancy
35
Q

what are some of the clinical findings associated with essential thrombocytosis?

A
  • high platelet count
  • large platelets on blood smear
  • abnormal platelet function
  • splenomegaly
  • abnormal WBCs and/or Hb/Hct
  • bleeding or thrombosis

HemOnc Week 2 (14 decks)

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