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HEM Exam 1 > Porphyria > Flashcards

Porphyria Flashcards

1
Q

definition of porphyrias

A
  • a group of metabolic disorders resulting from a mutation in one of the enzymes in the heme biosynthetic pathway
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2
Q

what are porphyrins

A
    • the toxic metabolites produced from the heme biochemical pathway
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3
Q

can porphyrins be cleared?

A
  • no
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4
Q

why can porphyrins not be cleared?

A
  • due to deficient enzyme action
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5
Q

function of porphyrins

A
  • no useful function

- act as highly reactive oxidants and damage tissues

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6
Q

heme is a part of

A
  • hemoglobin
  • myglobin
  • catalase
  • peroxidases
  • cytochromes
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7
Q

where is heme made?

A
  • 85% in erythroid cells

- rest in liver

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8
Q

what is heme used to make

A
  • P450 enzymes
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9
Q

first enzyme in heme synthesis pathway

A
  • ALA synthetase (ALAS)
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10
Q

importance of ALAS

A
  • first and rate limiting enzyme
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11
Q

what induces ALAS

A
  • increased demand for heme
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12
Q

what down regulates ALAS

A
  • the heme molecule

- by feedback inhibition

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13
Q

role of ALAS

A
  • catalyzes conversion of glycine and succinyl CoA

- forms delta-aminolevulinic acid

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14
Q

co-factor required by ALAS

A
  • pyridoxal-5-phosphate
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15
Q

things that induces ALAS

A
  • depletion of hepatic pool of heme
  • drugs, hormones that induce CYPs and ALAS1
  • caloric and carbohydrate restriction
  • metabolic stress
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16
Q

role of metabolic stress in inducing ALAS

A
  • may induce heme oxygenase and accelerate heme destruction
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17
Q

commonality of acute intermittent porphyria

A
  • most common acute porphyria
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18
Q

acute intermittent porphyria due to deficiency in

A
  • hepatic PBG deaminase

- hydroxymethylbilane synthase

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19
Q

acute intermittent porphyria genetic pattern

A
  • autosomal dominant

- incomplete (low) penetrance

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20
Q

acute intermittent porphyria - effect on erythrocyte PBG deaminase activity in affected individuals

A
  • 50% reduction
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21
Q

acute intermittent porphyria - when does it appear

A
  • latent prior to puberty
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22
Q

acute intermittent porphyria - in males or females?

A
  • symptoms more common in females
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23
Q

acute intermittent porphyria - what levels are increased during crisis?

A
  • urinary ALA

- PBG

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24
Q

reaction that PBG deaminase catalyzes

A
  • PBG -> hydroxymethylbilane
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25
Q

acute intermittent porphyria - what is primarily increased by environmental and other factors that increase disease severity

A
  • ALAS1
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26
Q

does acute intermittent porphyria always develop in all individuals with the mutation?

A
  • no
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27
Q

enzyme levels in acute intermittent porphyria

A
  • low PBGD activity

- induction of ALAS1

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28
Q

GI symptoms of acute intermittent porphyria acute attack

A
  • abdominal pain

- no inflammatory signs

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29
Q

most common feature of acute intermittent porphyria acute attack

A
  • abdominal pain
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30
Q

no inflammatory signs means

A
  • no elevated WBC
  • no fever
  • no rebound tenderness
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31
Q

peripheral neuropathy symptoms of acute intermittent porphyria

A
  • sensory and motor neuropathy

- may precede abdominal pain

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32
Q

acute intermittent porphyria- motor peripheral neuropathy in prolonged attacks

A
  • involve cranial nerves

- lead to bulbar paralysis, respiratory impairment, death

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33
Q

acute intermittent porphyria - autonomic nervous system features

A
  • elevated catecholamines
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34
Q

acute intermittent porphyria - elevated catechomaines cause

A
  • elevated heart rate

- elevated blood pressure

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35
Q

acute intermittent porphyria - neuropsychiatric findings

A
  • insomnia
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36
Q

acute intermittent porphyria - CNS involvement

A
  • seizures
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37
Q

acute intermittent porphyria - hypothalamus features

A
  • SAIDH

- hyponatremia

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38
Q

what is hyponatremia?

A
  • low sodium
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39
Q

acute intermittent porphyria - GU symptoms

A
  • dark or reddish brown urine
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40
Q

acute intermittent porphyria - abnormal color of urine due to

A
  • accumulation of porphyrins or porphyrin precursors
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41
Q

abnormal urine color between attacks

A
  • may lessen or return to normal
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42
Q

acute intermittent porphyria - exacerbating factors of an acute attack

A
  • drugs
  • crash diets
  • endogenous hormones
  • cigarette smoking
  • metabolic stresses
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43
Q

acute intermittent porphyria - exacerbating factors of acute attack - which drugs?

A
  • drugs that increase demand for hepatic heme

- cytochrome P450 enzymes

44
Q

acute intermittent porphyria - crash diets

A
  • decreased carb intake
45
Q

acute intermittent porphyria - endogenous hormones

A
  • progesterone
46
Q

acute intermittent porphyria - cigarette smoking

A
  • induces cytochrome P450
47
Q

acute intermittent porphyria metabolic stresses

A
  • infections, surgery, psychological stress
48
Q

acute intermittent porphyria - making the diagnosis

A
  • send urine for PBG and ALA during acute exacerbation
49
Q

if PBG and ALA during acute exacerbation are not elevated

50
Q

if PBG and ALA are markedly elevated

A
  • send PBG deaminase activity
51
Q

acute intermittent porphyria - treatment of acute attack

A
  • hospitalization
  • withdraw unsafe meds
  • IV 10% glucose
  • IV hematin ASAP
52
Q

how much 10% IV glucose do you give?

A
  • 300 g per day
53
Q

what do you give for treatment of crisis and prevention of attacks?

A
  • Cimetidine
54
Q

mechanism of action of hematin

A
  • reduces production of ALA/porphyrins by negative feedback inhibition on ALA synthase
55
Q

adverse reactions with hematin due to

A
  • degradation products binding to endothelial cells, platelets, and coagulation factors
56
Q

adverse reactions of hematin

A
  • thrombophlebitis
  • anticoagulation (inc PT)
  • thrombocytopenia
  • iron overload with repeated use
57
Q

porphyria cutanea tarda caused by

A
  • deficiency of UROD (uroporphyrinogen decarboxylase)
58
Q

60% of PCT patients

A
  • male

- drink alcohol

59
Q

women who develop PCT

A
  • often on estrogen containing meds
60
Q

age of most patients with PCT

61
Q

66% of patients with PCT have evidence of

A
  • iron overload
62
Q

reaction catalyzed by UROD

A
  • uroporphrinogen lII -> coproprophyrinogen III
63
Q

pathogenesis of PCT

A
  • iron overload leads to reduced activity of UROD enzyme

- leads to elevated uroporphyrin levels

64
Q

what levels are correlated with PCT

A
  • hepatic iron levels
65
Q

PCT association with up regulation of ALAS1 synthase

A
  • does not appear to be associated with
66
Q

associated disorders with PCT

A
  • alcoholism
  • hemochromatosis
  • hepatitis C
67
Q

skin findings of PCT

A
  • blisters
  • bullae
  • hyper and hypopigmentation
  • also hirsutism

ON SUN EXPOSED AREAS OF THE BODY

68
Q

bullae contains

A
  • porphyrin rich serious or sersanguinous fluid

- may be painful or become infected

69
Q

PCT liver enzymes

A
  • AST and ALT elevated
70
Q

PCT at an increased risk for these liver disorders

A
  • cirrhosis

- hepatocellular carcinoma

71
Q

PCT diagnosis

A
  • screening test

- confirmatory testing

72
Q

PCT screening test tests for

A
  • total plasma porphyrin levels
73
Q

PCT ALA and PBG levels

A
  • normal

- ALAS1 not induced

74
Q

PCT confirmatory testing tests for

A
  • more specific levels of urinary porphyrins to speciate the porphyria
75
Q

PCT treatment

A
  • remove offending agents
  • cover sun exposed areas
  • start phlebotomy
76
Q

offending agents of PCT

A
  • no alcohol
  • withhold estrogen
  • stop smoking
77
Q

what does phlebotomy for PCT do?

A
  • removes iron sequentially
78
Q

lead poisoning - blood levels in adults

A

> 10 mcg/dL

79
Q

lead poisoning - blood levels in children

A

> 5 mcg/dL

80
Q

level of safe lead in children?

81
Q

sources of lead for adults

A
  • leaded gasoline
  • lead paint
  • moonshine
  • workplace exposures
  • mining
  • firing ranges
82
Q

sources of lead in children

A
  • prenantal exposure

- ingestion

83
Q

some ingestion sources of lead in children

A
  • paint
  • water
  • food
  • soil
84
Q

primary source of lead exposure in children

A
  • lead-containing dust
85
Q

lead in drinking water compared to lead in food

A
  • absorbed more than lead in food
86
Q

major route of lead toxicity in adults

A
  • inhalation
87
Q

major route of lead toxicity in children

88
Q

when is lead released from the bone?

A
  • high bone turnover
89
Q

examples of high bone turnover

A
  • pregnancy
  • hyperthyroidism
  • menopause
  • breast feeding
90
Q

lead’s biochemical and cellular effects

A
  • inhibits sulfhydryl groups in RBC enzymes ALAS and ferrochelatase in the heme synthetic pathway
91
Q

blockage of pyrimidine 5’ nucleotidase causes

A
  • degradation of ribosomal RNA in red blood cells

- leads to basophilic stippling

92
Q

basophilic stippling associated with

A
  • RNA instability
93
Q

acute effects of lead toxicity

A
  • GI
  • anemia
  • neurologic
  • muscle and joint pain
  • lead line
94
Q

GI effects of lead toxicity

A
  • lead colic - crampy abdominal pain
95
Q

type of anemia in lead toxicity

A
  • microcytic
96
Q

classic neurological finding in lead toxicity

A
  • wrist and foot drop
97
Q

what is lead line?

A
  • classic finding of bluish discoloration of the gums

- lead reacts with plague at the gumline

98
Q

neuropsychiatric effects of chronic lead exposure

A
  • declines in neurocognitive function
  • psychiatric symptoms
  • distal sensory and motor neuropathy
  • EKG conduction delay
  • decreased hearing acuity
99
Q

lead nephropathy

A
  • increased hypertension and gout

- saturnine gout

100
Q

diagnosing lead toxicity

A
  • blood lead levels

- FEP and ZPP levels

101
Q

blood lead levels

A
  • key clinical monitoring test for diagnosing lead toxicity
102
Q

what kind of stick for blood lead levels

A
  • venous stick
103
Q

FEP and ZPP levels

A
  • indicator of lead exposure and effect over previous 3 month period
104
Q

if FEP and ZPP levels are elevated

A
  • do CBC

- renal function testing

105
Q

management of lead toxicity

A
  • reduce lead exposure

- chelation therapy

106
Q

when should chelation be undertaken

A
  • only when exposure has been definitively curtailed
107
Q

bad use of chelation

A
  • use could result in enhanced absorption of lead and worsening toxicity

HEM Exam 1 (22 decks)

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