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S3B5 Pathology > Platelet Abnormalities > Flashcards

Platelet Abnormalities Flashcards

1
Q

What platelet abnormality is often seen in individuals who have been on a by-pass machine?

A

platelets get degranulated by the by-pass machine- so may have an acquired platelet dysfunction when they come out of surgery

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2
Q

What is the platelet function in primary hemostasis?

A
  • vessel injury
    • exposure of collage & vWF
  • platelet adhesion
  • platelet activation
  • platelet aggregation
  • primary hemostatic plug
  • stabilized by fibrin meshwork
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3
Q

What clinical findings are seen in platelet dysfunction or thrombocytopenia?

A
  • petechiae
  • ecchymoses
  • epistaxis
  • menorrhagia
  • GI hemorrhage
  • Gingival bleeding
  • Post-partum hemorrhage
  • post-operative bleeding
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4
Q

Identify the different types of bruising seen in the provided image. These symptoms are seen in what conditions?

A

platelet dysfunction or thrombocytopenia

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5
Q

What are the type of thrombocytopenia?

A
  • decreased production
  • decreased survival
  • sequestration
  • dilution
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6
Q

What are the types of thrombocytosis?

A
  • reactive
    • infectious/trauma
    • iron deficiency
    • carcinoma
    • exercise
  • neoplastic
    • myeloproliferative
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7
Q

What are the causes of defective platelet function & associated conditions?

A
  • defective adhesion (Benard-Soulier)
  • defective aggregation (Glanzmann thrombasthenia)
  • defective secretion (storage pool disorder)
  • liver disease
  • uremia
  • drug
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8
Q

What is Mey-Hegglin Anomaly?

Inheritance pattern?

Peripheral blood smear?

A

hereditary thrombocytopenia disorder

autosomal dominant

normal platelet function & not associated with bleeding

  • mild thrombocytopenia
  • large platelets
  • Dohle-like bodies in leukocytes
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9
Q

What mutation is seen in Benard-Soulier syndrome?

A

mutation in GPIb, which causes a decreased membrane GPIb-V-IX (receptor for vWF & is necessary for platelet adhesion)

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10
Q

Bernard-Soulier syndrome causes what type of platelet dysfunction?

inheritance pattern?

Peripheral blood smear?

A

defective adhesion after injury -moderate to severe bleeding

autosomal recessive

  • platelets are large (like May-Hegglin, but these have impaired function)
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11
Q

The provided smear could be from what two conditions? How could you tell them apart?

A

large platelets

May-Hegglin Anomaly (platelets are functional)

Benard-Soulier syndrome (impaired adhesion)

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12
Q

What mutation is seen in Glanzmann Thrombasthenia?

A

deficiency or dysfunction in GPIIb/IIIa, a protein that binds to fibrinogen & vWF during platelet adhesion & aggregation

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13
Q

Glanzmann Thrombasthenia causes what type of platelet dysfunction?

inheritance pattern?

Peripheral blood smear?

A

defective platelet aggregation in homozygotes (heterozygotes are asymptomatic)

autosomal recessive

  • normal platelet count & morphology but abnormal function
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14
Q

What CBC values do you see in a patient with Primary Immune Thrombocytopenic purpura (ITP)?

A
  • severe (<20K) thrombocytopenia
    • often large, immature platelets
  • all other counts are normal
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15
Q

What is the clinical presentation of a patient with chronic Primary Immune Thrombocytopenic purpura?

Treatment?

A
  • Female 20-40yr
  • insidious onset
    • mucocutaneous bleeding
  • NO systemic symptoms
  • NO splenomegaly
  • Treatment
    • corticosteroids, IVIg & sometimes splenectomy
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16
Q

What is the cause of chronic Primary Immune Thrombocytopenia (ITP)?

A

autoantibodies against platelet antigen → peripheral destruction

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17
Q

Why is it not helpful to test for anti-platelet antibodies in the diagnosis of ITP?

A

it is not sensitive nor specific

negative result does not rule out ITP

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18
Q

What is the cause of acute ITP?

A

IgG antibodies directed against GP IIb-IIIa on platelets

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19
Q

What is the clinical presentation of a patient with acute ITP?

A

usually young child

abrupt onset - triggered by viral infection (1-3 weeks prior)

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20
Q

Secondary ITP is associated with what conditions?

A

autoimmune diseases, lymphomas, viral infections (HIV, HepC) & drugs (quinidine, heparin)

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21
Q

What is the definition of RBC fragmentation syndrome with thormbocytopenia?

A

non-immune hemolytic anemia resulting from intravascular RBC fragmentation, usually within small arterioles & capillaries - possibly from artificial heart valves or ventricular assist devices

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22
Q

What is disseminated intravascular coagulation?

A

formation widespread microvascular thrombi after activationof coagulation cascade by tissue factor or mimic, resulting in microangiopathic hemolytic anemia & thrombocytopenia

body degrades newly formed fibrin → consumptive coagulopathy & bleeding diathesis

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23
Q

What laboratory values will you see in patient with DIC?

A

PT, PTT, & TT may be prolonged (sometimes normal in early stages)

low fibrinogen

elevated D-dimer

elevated FDP

24
Q

What peripheral blood findings are consistent with DIC?

A

schistocytes

25
Q

What are the causes of DIC?

A

major trauma (crush)

overwhelming infections

obstetric complications

mucin-secreting adenocarcinomas

prostatic surgery

venomous snake bites

26
Q

What is the treatment for DIC?

A

eliminate underlying cause

supportive therapy

26
Q

What is the treatment for DIC?

A

eliminate underlying cause

supportive therapy

27
Q

What are the the characteristics of the related Thrombotic Microangiopathies (TTP/HUS)?

A

diffuse microvascular occlusion of arterioles & capillaries by thrombi - mainly by platelets not fibrin

leading to blood schistocytosis, ischemia, & end organ damage

no perivascular inflammation

28
Q

TTP & HUS usually have what type of coagulation screening tests?

A

usually normal

29
Q

Thrombotic Thrombocytopenic Purpura is characterized by what features?

A
  • severe thrombocytopenia (<20,000)
  • microangiopathic hemolytic anemia (schistocytes)
  • neurologic symptoms
  • fever
  • increased serum LDH
30
Q

What symptoms is seen more commonly in TTP than other types of TMA?

A

systemic manifestation of organ damage (besides kidneys)

31
Q

What are the two types of TTP?

Which is more common?

Age group most commonly affected by each?

A

inherited - uncommon (infancy & childhood - remits & relaplse)

acquired - adults & older children - single acute episode

32
Q

What molecular deficiency is seen in TTP? How does this lead to its clinical presentation?

A
  • Severe deficiency (<10%) ADAMTS13, which is responsible for cutting vWF into smaller, less reactive multimers
  • Patients with this deficiency release ultra-large von Wilibrand multimers (ULvWF) after endothelial damage, leading to exuberant formation of platelet microthrombi in microcirculation
33
Q

What laboratory features are consistent with TTP?

A
  • schistocytes
  • thrombocytopenia
  • increased LDH
  • coagulation tests are usually normal
34
Q

What is the treatment for TTP?

A

emergent plasma apheresis with FFP or cryo-poor plasma

NO PLATELETS UNLESS LIFE-THREATENING BLEEDING

35
Q

Hemolytic Uremic Syndrome is characterized by what features?

A
  • microangiopathic hemolytic anemia
  • thrombocytopenia
  • acute renal failure
  • +/- diarrhea
  • CNS symptoms
36
Q

What are the two types of Hemolytic Uremic Syndrome?

A
  • primary “atypical” - complement dysregulation
    • complement gene mutations
    • antibodies to complement factor H
  • secondary
    • infection (shiga toxin)
    • drug toxicity
    • rarely - pregnancy & autoimmune
37
Q

Does TTP or HUS have a lower mortality rate?

A

HUS has a lower mortality rate than TTP

38
Q

What is the most common cause of HUS?

A

E. coli O157:H7

via contaminated hamburger

39
Q

What is the treatment for HUS?

A

supportive - with dialysis

40
Q

What is a common complication of unfractionated heparin?

A

life-treatening venous or arterial thrombosis

41
Q

What are the two types of Heparin-Induced Thrombocytopenia (HIT)? What are their different features & clinical significance?

A
  • Type I
    • rapidly after administration
    • direct platelet-aggregating
    • usually little clinical significance
  • Type II
    • 5-14 days after administration
    • autoantibodies to a complex of heparin & low molecular weight proteins (platelet factor 4), which activates platelets and leads to thrombocytopenia & thrombosis
    • Thrombi in arteries & veins
42
Q

What value should you be sure to check before stating someone on heparin?

A

platelet

43
Q

What are two major clues to the presence of HIT?

A
  1. fall in platelet count 1-2 weeks after starting heparin
  2. unexpected shortening of aPTT
    1. still prolonged, b/c on heparin, but shorter than expected
44
Q

What differential diagnoses must be ruled out as a cause of thrombocytopenia before making a diagnosis of HIT?

A

bleeding, infection, hemodilution

45
Q

How do you confirm the diagnosis of HIT?

A

heparin-platelet antibody assay

do not wait for results to start therapy

46
Q

What is the treatment for HIT?

A

stop heparin - use different anticoagulant (NOT low molecular weight heparin)

avoid giving platelets

47
Q

What is the most common cause of drug induced acquired disorder or platelet function?

A

aspirin

(NSAID, penicillins, hydroxychloroquine, amitriptyline, etc)

48
Q

What are common causes of acquired disorders of platelet dysfunction other than drug-induced?

A

liver disease

uremia (reversible)

bypass surgery

autoimmune disorders

hematolymphoid neoplasms

49
Q

Aspirin impacts what molecule that leads to impairment of primary hemostasis?

A

acetylates platelet COX → impairs prostaglandin metabolism → impairs synthesis of thromboxane A2 → impairs thromboxane A-2-dependent platelet aggregation (primary hemostasis)

50
Q

How does aspirin affect the coagulation cascade?

A

aspirin has no effect on the coagulation cascade

51
Q

What effects does uremia have on platelet function?

A
  • defects in adhesion
  • decreased synthesis of thromboxane A2
  • possibly circulating metabolites or toxins inhibit platelet function
52
Q

What is the treatment for uremia-induced platelet dysfunction?

A

dialysis

DDAVP (vasopressin)

estrogens

53
Q

What effects does liver diseasehave on platelet function?

A
  • multifactorial
  • FDP compromise platelet function & impair release of platelet factor 3
54
Q

What effects does bypass surgery have on platelet function?

A
  • cause thrombocytopenia & platelet dysfunction secondary to depletion of platelet dense granules & alpha granules
55
Q

What are the common causes of pseudothrombocytopenia?

A

platelet aggregates from traumatic blood draw or inadequate mixing

EDTA-induced aggregation (draw in heparinzed tube)

56
Q

After a CBC indicates thrombocytopenia, what step should occur before starting the transfusion?

A

peripheral blood smear review by technologist to look for platelet clumps & satelliotisis where platelets accumulate around WBC

S3B5 Pathology (13 decks)

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