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ACEM pathology > 14 part 2 Bleeding Disorders > Flashcards

14 part 2 Bleeding Disorders Flashcards

1
Q

What does bleeding time measure?

A

platelet response to a LIMITED vascular injury

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2
Q

What will make bleeding time abnormal?

A

deficit in platelet number or function

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3
Q

What test assesses the function of the extrinisic and common pathways?

A

Prothrombbin Time

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4
Q

What will be elevated with deficiencies in factor VII and /or factors X, V, prothrombin II and fibrinogen I?

A

PT

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5
Q

What test assesses the intrinsic and common pathways?

A

Partial Thromboplastin Time (PTT)

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6
Q

What will cause elevation of PTT?

A

deficiciencies in factors VIII, IX, XI, XII and or factors X,V, Pro II, and fib I

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7
Q

What is a normal platelet count?

A

150000 - 450000/mm3

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8
Q

If platelet count is abnormal, what should be done?

A

do PB smear to rule out false thrombocytopenia

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9
Q

What is a normal PT?

A

10-13 sec

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10
Q

What is a normal PTT?

A

25-35 sec

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11
Q

What are used to clot in plasma for PTT?

A

kaolin, cephalin, and Ca

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12
Q

What can clue to bleeding due to vessel wall abnormalities?

A

petechiae and purpura

normal PTT and PT

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13
Q

What microbes can cause vasculitis or DIC?

A

menigococcus, IE orgs (strep/staph) and rickettsia

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14
Q

What is a particular term for the kind of hypersensitvity vasculaitis that occurs with drug reactions?

A

leukocytoclastic

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15
Q

What happens in Ehler-Danlos syndrome?

A

imparied collagen around the vessel walls causes hemorrhage

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16
Q

How is cushing syndrome similar to Ehlers-Danlos?

A

loss of perivascular support tissue, but this is due to the protein wasting effects of corticosteroids

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17
Q

What is the name of a vessel wall abnormality that is described by systemic hypersensitvity disease of unknown etiology, which manifests as purpura, colic, polyarhtralgia, and acute glomerulonephritis?

A

Henoch-Schonlein purpura

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18
Q

What is the mechanism of Sx seen in Hencoh-Schonlein purpura?

A

immune complex deposition on vessels and glomeruli

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19
Q

WHat is the name for an autosomal dominant vascular disorder, that causes bleeding in dialted, tortuous, thin walled vessels, and manifests primarily in the mucous mambranes of the nose, mouth, and eyes and GI tract mucosa?

A

Hereditary Hemorrhagic Telangiectasia

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20
Q

What protein is deposited, systemically, from plasma cells in primary amyloidosis?

A

AL protein

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21
Q

Which two tests are ususally normal in the setting of thrombocytopenia?

A

PT and PTT

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22
Q

What can occur at a platelet count of <20,000?

A

spontaneous bleeding

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23
Q

What affect do megalolastic anemias have on platelet production?

A

ineffective megakaryocyte production

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24
Q

How long are platelets viable in transfusable blood?

A

24 hours

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25
Q

What happens in immune thrombocytopenic purpura?

A

Chronic ITP
IgG antibodies form against platelet membrane glycoproteins Iib-IIIa or Ib-IX
Opsonised platelets are then phagocytosed by mononuclear phagocytes – spleen is the major site of removal
There is some evidence to suggest magakarycocyte injury or destruction but this is minor

Acute ITP
Typically preceeded by a viral illness 2 weeks prior

Normal size spleen Congested sinusoids Hyperactivity and enlargement of splenic follicles
Bone marrow has increased megakaryocytes

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26
Q

What secondary conditions can cause ITP?

A

SLE, AIDS, viral infection, drugs

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27
Q

What is the priamry Ab made against platelets in ITP?

A

Chronic ITP
IgG antibodies form against platelet membrane glycoproteins Iib-IIIa or Ib-IX
Opsonised platelets are then phagocytosed by mononuclear phagocytes – spleen is the major site of removal
There is some evidence to suggest magakarycocyte injury or destruction but this is minor

Acute ITP
Typically preceeded by a viral illness 2 weeks prior

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28
Q

What does IgG do to platelets after binding in ITP?

A

opsonizes them

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29
Q

What is the main treatment for ITP?

A

splenectomy

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30
Q

What test is important in considering differential diagnosis in ITP?

A

BM Bx to rule out marrow failure

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31
Q

What is seen in the spleen in ITP?

A

mild snusoidal congestion with megs in sinuses

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32
Q

What besides primary morpholgy can clue to ITP?

A

secondary bleeding in any part of the body

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33
Q

In what patient population is Idiopathic TP more likely?

A

Chronic ITP
Most common in women less than 40 years
Female to male 3:1

Acute ITP
Childhood disease preceeded by acute viral infection

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34
Q

What do platelets in a PB smear of a patient with ITP look like?

A

large

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35
Q

What population of patients does acute ITP occur in?

A

abrupt onset after viral illness in childhood

usually 2 wk interval between infection and purpura

Abrupt onset Usually self limiting (lasts less than 6 months) 20% go on to develop chronic ITP

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36
Q

In acute ITP, what % go on to have chronic ITP?

A

~20%

Chronic ITP-
Insidious onset
Characteristic long history of nose bleeds, easy bruising
Bleeding time prolonged PT and APTT normal

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37
Q

What drugs are notable for TP risk?

A

quinine, quinidine, sulfonamides, and heparin

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38
Q

How many patients are reciving heparin?

A

1/20

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39
Q

What is the most common drug induced TP?

A

type I heparin induced

abrupt
moderate severity
usually clinically insignificant

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40
Q

Which type of drug induced TP is life threatening?

A

type II

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41
Q

What is the mechanism of type II heparing induced TP?

A

heparin/platelet factor IV complex reaction

Factor IV binds and activates paltelets whcih leads to thrombosis

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42
Q

What is the onset of Type II drug TP?

A

delayed onset of 5-14 days

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43
Q

What is the most common hematologic probem in HIV?

A

thrombocytopenia

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44
Q

What happens in HIV induced TP?

A

increased destruction and decreased production

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45
Q

WHat 2 mechanisms are possible causes of HIV induced TP?

A

Megs have CD4 receptors

platelet membrane GP Abs (IIb-IIIa)

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46
Q

What adult disease, exhibiting transient neuro deficits and in the setting of some renal failure, has the mechanism of a ADAMTS 13 enzymatic deficieny?

A

TTP

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47
Q

What does ADAMTS 13 normally do when present in adequate amounts?

A

degardes HMWK multimers of vWF promoting platelet microaggregation

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48
Q

What therapy has increased recovery to >80% in TTP?

A

plasma exchange therapy

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49
Q

What close cousin of TTP ususally occurs in children but does not produce neuro deficits and has a course that is dominated by acute renal failure?

A

HUS

50
Q

What bacterial infection often precedes an episode of HUS?

A

E. Coli (o157:H7) producing gastroenteritis

51
Q

What can be sometimes irreversible in sever cases of HUS?

A

renal damage

52
Q

Why does HUS ususally happen in adults?

A

secondary to drugs and/or radiation therapy

53
Q

What is the usual patholgy of HUS in adults?

A

endothelial cell damage that leads to platelet microaggregate formation

prognosisis guarded

54
Q

What two bleeding disorders share the following cahracteristics:

wide spread thrombi of dense platelets in microcirculation

decreased platelet count

increased bleeding time

NORMAL PT and PTT?

A

TTP and HUS

55
Q

Why do ASA and NSAIDs prolong bleeding time?

A

inhibition of cyclooxygenase which suppresses TXA2 and PG synthesis

56
Q

Why does uremia cause platelet dysfxn?

A

not really known

57
Q

What defects occur in congential platelet dysfxn?

A

disorders of :

adhesion
aggregation
secretion

58
Q

What is the name of an AR inherited deficiency of platelet membrane GP complex Ib-IX (vWF receptor), that causes defective adhesion to subendothelial collagen?

A

Bernard-Soulier syandrome

59
Q

What is the name of the AR deficiency of platelet memebrane GP complex IIb-IIIa?

A

Glanzmann thrombasthenia

60
Q

What is the normal fxn of GP complex IIb-IIIa?

A

create fibrinogen bridges between platelets

61
Q

What are “thrombasthenic platelets” unable to do?

A

cannot aggregate with ADP, collagen, epinephrine or thrombin

62
Q

What is the ususal problem in platlet secretion dysfxn?

A

impaired secretion of alpha and dense core granules

63
Q

What are normally contained in alpha and dense core granules?

A

ADP, TXAs

64
Q

What are uncommon in clotting factor abnormalities?

A

petechiae and purpura

65
Q

What are common clinical features of clotting factor abnormalities?

A

ecchymoses or hematomas post trauma

prolonged post op bleeds

GI or GU bleeds

hemorrhage of weight bearing joints

66
Q

What acquired clotting factor abnormality causes decreased II, VII, IX, and X levelas as well as decreased protein C levels?

A

vitamin K deficiency

67
Q

What is deficient in Hemophilia A?

A

factor VIII

68
Q

What factor is deficient in Hemophilia B?

A

factor IX

69
Q

Where is factor VIII made?

A

liver and kidney

70
Q

Why is factor VIII necessary?

A

factor X activation

71
Q

Which is larger VIII or vWF?

A

vWF

72
Q

Where is vWF made?

A

endothelial cells and Megs

73
Q

What is the main job of vWF?

A

binding to collagen, heparin, and platelet membrane GPs to promote hemostasis

74
Q

What carries and stabilizaes factor VIII?

A

vWF

75
Q

What happens to factor VIII in the absensce or deficiency of vWF?

A

t1/2 is decreased by 80%

76
Q

How can vWF be measured?

A

ristocetin agglutination test

Forms a complex with factor VIII – factor VII required for factor X activation Facilitatesthe adhesion of platelets to endothelium via platelet GpIb-IX

77
Q

Is vWF common?

A

yes, very

frequency of ~1%

Prolonged bleeding time, normal platelet count
Characterised by excessive bleeding from wounds, menorrhagia, spontaneous mucous membrane bleeding

78
Q

How is vWF inherited?

A

AD

Several variants
Type 1 and 3 have reduced quantities
Type 2 has VWF with functional defects

VWF produced by endothelial cells

Functions
Forms a complex with factor VIII – factor VII required for factor X activation Facilitatesthe adhesion of platelets to endothelium via platelet GpIb-IX

79
Q

What is wrong with vWF in VWD?

A

low quality or quantity of vWF

One of the most common inherited disorders of bleeding in humans
1% frequency

80
Q

What are the clinical features of vWD?

A

spontaneous mucous membrane bleeds

excess bleed from wound or menorrhagia

81
Q

Why is blleding time prolonged in vWD?

A

platelats cannot adhere to subendothelial collagen with out vWF

82
Q

Why is PTT prolonged in vWD?

A

without vWF, factor VIII has avery short t1/2

83
Q

Which vWD types exhibit low quantity of vWF?

A

types 1 and 3

84
Q

Which type of vWD exhibits a qualitative defect in vWF?

A

type 2

85
Q

Which type of vWD is AD, mild, and represents 70% of most vWD cases?

A

type 1

86
Q

Which type of vWD is AR, severe and may clinically resemble Hemophila ?

A

type 3

87
Q

Which subset of type 2 vWD is most common?

A

2A

88
Q

What is the inheritance pattern of vWD type 2?

A

AD, causing missense mutations

89
Q

What is missing from the plasma in type 2 vWD?

A

large and intermediate multimers that contribute to vWF?

90
Q

What is the most common hereditary diease with SERIOUS bleeding?

A

Hemophilia A

91
Q

What is the inheritance pattern of Hemophilia A?

A

X linked recessive: Mostly occurs in males and homozygous females
Can occur in heterozygous females if there is unfavourable lyonisation

30% no family hx

92
Q

Why are there few hetero Hemo A females?

A

lyonization of normal X

93
Q

What is the pathology of Hemo A?

A

reduced quantity or activity of factor VIII

Clinical effect correlates with level of factor VIII
<1% severe 2-5% - moderate 6-50% - mild

94
Q

WHat % of patients with Hemo A have no family history (new mutation)?

A

30%

95
Q

Upon what does the severity of Hemo A depend?

A

the activity level of factor VIII

96
Q

Upon what does the activity level of factor VIII depend?

A

the type of mutation

97
Q

When can hemarthrosis occur in type A hemophiliacs?

A

everyday wear and tear

98
Q

What is the effect of Hemo A on bleeding time, platelet count, and PT?

A

none

99
Q

What pathway will be affected by Hemo A, how does this show?

A

intrinsic path, shows by prolonged PTT

100
Q

How is Hemo A diagnosed?

A

factor VIII assay

101
Q

How is Hemo A treated?

A

infusion of recombiant factor VIII

102
Q

What can happen in 15% of hemo A patients during a course of traetment?

A

Factor VIII Ab development

103
Q

What is the inheritance pattern of Hemo B?

A

X-linked recessive

104
Q

How many Hemo B patients have normal levels or NONFUNCTIONAL factor IX?

A

1/7

In 14% factor IX is present but non- functional

105
Q

What is generally the only way to differntiate Hemo A from Hemo B if severe?

A

do a factor IX assay

106
Q

What is the general concept behind DIC?

A

consumption of platelets, fibrin and coagulation factors causes microthrombi, while secondary fibrinollysis causes hemorrhage

107
Q

What are the two triggering mechanisms of DIC?

A

tissue factor or thromboplastic substance release

widespread endothelial injury

108
Q

What do the following substances have in common?

placenta
adenocarcinomic mucus
leukemic cell granules
gram - endotoxin
tissue thromboplastins
A

these are all tissue factor/thromboplastic substances

109
Q

WHat cytokine causes endothelial cell injury in septic shock?

A

TNF

110
Q

What event initiates TF release, promotes platelet aggregation and activates the intrinsic pathway?

A

endothelial cell injury

Initiating mechanisms
Release of tissue factor or thromboplastic substances into the circulation Widespread injury to endothelial cells

Consequences:
Fibrin deposition in microcirculation Ischaemic injury
Microangiopathic haemolytic anaemia
Activation of plasmin Haemorrhagic diathesis due to consumption of clotting factors

111
Q

What is the most frequent cause of DIC?

A

obstetric complications

50% are obstetric patients
33% have carcinomatosis (DIC tends to develop insidiously)

112
Q

Why does hemolytic anemia result from widespread fibrin deposits in the microcirculation?

A

RBC fragmentation in the narrowed microvasculature

113
Q

What does FDP do?

A

inhibits platelet aggregation and fibrin polymerization

114
Q

What is a severe occurrence that can be seen in the kdneys as aresult if DIC?

A

bilateral renal cortical necrosis

115
Q

What can happen to the adrenal glands in the setting of meningococcemia, secondary to fibrin microthrombi?

A

massive adrenal hemorrhage

116
Q

What is Sheehan syndrome?

A

anterior pituitary necrosis occurring as a result of severe peripartum bleed

117
Q

What is the ususal presentation of acute DIC?

A

bleeding as a result of obstetric complications or trauma

118
Q

What is the usual presentation of chronic DIC?

A

thrombotic complications as a result of a carcinomatosis

119
Q 
What classification of DIC presents with thrombocytopenia
decreased fibrinogen
prolonged PT and PTT
and
Elevated FSP?
A

severe acute DIC

120
Q

How can acute mild DIC be differntiated from severe on the lab work?

A

in acute mild DIC, PT and PTT may be normal

ACEM pathology (4 decks)

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