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IBI Test 4 > B3.067 Thrombocytopenia > Flashcards

B3.067 Thrombocytopenia Flashcards

1
Q

what are thrombotic microangiopathies (TMAs)

A

heterogeneous set of conditions linked by a common histopathologic finding of endothelial damage resulting in microvascular thromboses

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2
Q

what is microangiopathic hemolytic anemia (MAHA)

A

non-immune hemolytic anemia resulting from intravascular red cell fragmentation with schistocytosis

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3
Q

what is the result of TMAs

A

thrombocytopenia secondary to consumption

organ damage

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4
Q

how does TMA present on a renal biopsy

A

multiple thrombi observed in glomerular capillaries and in arterioles (red staining)

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5
Q

major causes of TMAs

A

thrombotic thrombocytopenic purpura (TTP)
hemolytic uremic syndrome (HUS)
misc (drugs, radiation, BMT, infections, autoimmune conditions)

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6
Q

subsets of HUS

A

typical: E.coli strain O157:H7 infection, endothelial damage by shiga like toxin
atypical: alternative complement pathway inhibitor deficiencies

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7
Q

pentad of TTP

A 
fever
thrombocytopenia
microangiopathic hemolytic anemia
transient neuro deficits
renal failure
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8
Q

deficiency associated with TTP

A

deficiency in plasma enzyme ADAMTS13 which normally degrades very high MW multimers of vWF
in absence of ADAMTS13, multimers accumulate in plasma and tend to promote platelet activation and aggregation

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9
Q

epidemiology of TTP

A 
incidence 0.04-0.004/1000
0.4/1000 in pregnant women
0.25-0.7/1000 among ticlopidine users (can stimulate production of Ab against ADAMTS13)
F:M is 1.5:1
highest in African American women
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10
Q

common causes/ risk factors of TTP

A 
def of ADAMTS13
-autoantibodies
-genetic mutations
ticlopidine/clopidogrel
HIV infection
autoimmune disorders
pregnancy
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11
Q

diagnostic testing for TTP

A 
CBC- Hb, Hct, platelet count
peripheral smear- schistocytes
LDH- elevated
bilirubin- elevated
PT, PTT, fibrinogen- normal
Coombs test- normal
BUN and creatinine- mild elevation
urinalysis- proteinuria, hematuria, leukocytes
confirmatory test for ADAMTS13 activity
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12
Q

differentiating sepsis from TTP

A

normal level of ADAMTS13

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13
Q

differentiating vasculitis from TTP

A

not usually associated with microthrombi or hemolytic anemia

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14
Q

what is vasculitis

A

inflammatory dysfunction of blood vessels in numerous organs that can be associated with anemia or thrombocytopenia

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15
Q

what is malignant hypertension

A

potentially life threatening disorder caused by organ damage as a result of severe high blood pressure

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16
Q

differentiating malignant hypertension from TTP

A

grade 3 or 4 retinopathy seen in malignant hypertension

17
Q

differentiating autoimmune hemolytic anemias from TTP

A

spherocytes rather than schistocytes

positive Coombs test

18
Q

differentiating immune thrombocytopenic purpura (ITP) from TTP

A

ITP does not have evidence of multisystem disease

19
Q

differentiating DIC from TTP

A

increased PT
decreased fibrinogen
increased fibrin degradation products and D-dimer
^^^in DIC

20
Q

first line treatment for TTP

A

plasma exchange

decreases mortality rate from 90% of patients to 10%

21
Q

discuss fresh frozen plasma for TTP

A

second choice therapy
should be done immediately
less effective than plasma exchange due to inability to deliver appropriate volumes

22
Q

splenectomy in TTP

A

reserved for refractory cases for patients who relapse

23
Q

what is atypical HUS

A

characterized by MAHA and thrombocytopenia, and prominent renal insufficiency
associated with defect in complement factor H, membrane cofactor protein (CD46), or factor I
hereditary or acquired (autoimmune antibodies)

24
Q

pathogenesis of atypical HUS

A

deficiency of complement regulator proteins leading to activation of alternative complement system
aberrant activation of alternative complement pathway
leads to endothelial damage

25
Q

acquired causes of atypical HUS

A 
s. pneumo
HIV
malignancies
systemic rheumatologic diseases
pregnancy
drugs (cyclosporine, tacrolimus)
stem cell transplant
26
Q

presentation of atypical HUS

A 
MAHA
thrombocytopenia
renal failure
no ab pain or diarrhea
neuro manifestations less common
27
Q

lab test results in atypical HUS

A 
CBC
peripheral  blood- schistocytes
LDH- elevated
bilirubin- elevated
PT, PTT, fibrinogen- normal
Coombs- negative
BUN and creatinine- markedly elevated
tests for complement and complement inhibitory proteins
negative culture for E.coli
ADAMTS13 > 10%
28
Q

diagnostic criteria of aHUS

A
  1. absence of other diseases associated with TMA
  2. no criteria for Stx-HUS
  3. no criteria for TTP
  4. measurement of C3 and C4, factors H, I, B, MCP and antibody for factor H
29
Q

treatment of aHUS

A

plasma therapy
eculizumab- neutralized Ab to C5
supportive therapy

IBI Test 4 (21 decks)

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