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Inborn Errors in Metabolism Flashcards

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1
Q

what is the general mechanism in IEM and three possible consequences?

A

block an enzyme

  1. substrate accumulates
  2. secondary metabolite accumulates
  3. decrease in product
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2
Q

what are the two categories of IEM and how is their Rx different?

A
  1. defects in energy sources (treat w/ diet)

2. defects in cellular organelles (difficult to treat)

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3
Q

why do IEMs typically present about a week after birth?

A

placenta allows for exchange of metabolites, but when neonate starts feeding toxic metabolites accumulate

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4
Q

what are the two main (general) presentations in IEM

A

acute decompensation

neurologic deterioration

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5
Q

what are common symptoms in neonates? (7)

A 
poor feeding
vomiting
lethargy
seizures
liver dysfunction
apnea 
abnormal odor
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6
Q

what are some common symptoms in infant/child? (8)

A 
failure to grow
recurrent vomiting
seizures
developmental delay
developmental regression
liver dysfunction
abnormal odor
yet...afebrile
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7
Q

when should you suspect IEM in neonates? children?

A

neonates w/ unexplained illness and normal pregnancy/delivery

children w/ acute unexplained deterioration with an illness

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8
Q

what are telltale clinical sign of IEM?

A

high ammonia, metabolic acidosis, hypoglycemia

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9
Q

There are ten lab tests that help. Name them

A 
electrolyte panel
blood glucose
ammonia
lactate
liver function
urine ketones
plasma AA
urine organic acids
plasma acylcarinitines
plasma carnitine
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10
Q

what does electrolyte panel tell you and what are possible disorders if abnormal?

A

acid base status, anion gap

organic acidemias

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11
Q

what does blood glucose tell you and what are possible disorders if abnormal?

A

can lead to change in mental status and acute illness

FA ox disorder

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12
Q

what does ammonia tell you and what are possible disorders if abnormal?

A

causes acute encaphalopathy

urea cycle disorders
organic acidemias

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13
Q

what does lactate tell you and what are possible disorders if abnormal?

A

errors in aerobic metabolism and gluconeogenesis

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14
Q

what does liver fxn test tell you and what are possible disorders if abnormal?

A

galactosemia can cause acute liver dmg

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15
Q

what does urine ketones tell you and what are possible disorders if abnormal?

A

organic acidemias = ketosis

FA ox disorder = hypoketotic

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16
Q

what does plasma AA tell you and what are possible disorders if abnormal?

A

diagnostic of aminoacidopathies

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17
Q

what does urine organic acids tell you and what are possible disorders if abnormal?

A

diagnostic of organic academies, FA ox, aminoacidopathies

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18
Q

what does plasma acylcarnitines tell you and what are possible disorders if abnormal?

A

organic acidemias, FA ox

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19
Q

what does plasma carnitine tell you and what are possible disorders if abnormal?

A

organic acidemias, fatty acid ox

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20
Q

What are some of the criteria for a disease to be included in newborn screening? (7)

A
  1. important health problem
  2. accepted treatment
  3. recognizable pre-symptomatic
  4. integrated program of education, testing, diagnostic confirmation, treatment, evaluation of outcome
  5. suitable test
  6. natural history of disease understood
  7. cost-benefit analysis
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21
Q

how are IEM typically inherited?

A

autosomal recessive

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22
Q

what are some of the characteristics of IEM inheritance? (5)

A 
allelic heterogeneity
locus heterogeneity
modifier genes
environmental factors
NBS -> early intervention -> changes natural history
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23
Q

Give two main aminoacidopathies and the enzyme that is deficient.

A

1 PKU. phenylalanine hydroxylase

2. MSUD. alpha-KB dehydrogenase

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24
Q

what is elevated/low in PKU?

Study These Flashcards
A

Phe, phenylacetate, phenyl pyruvate elevated

Tyr low

25
what are the symptoms of PKU if untreated in children (5)
``` severe MR seizures autistic like eczema light hair and complexion ```
26
what are symptoms of PKU if untreated in adults? (5)
``` lower cognitive skills executive function deficits increase psychological problems white matter injury maternal PKU syndrome ```
27
what are symptoms if PKU is treated?
normal growth and development
28
How do you treat PKU
Phe restriction w/ AA formula | Biopterin cofactor therapy
29
how does biopterin cofactor therapy work in PKU?
60% respond | Must have to have residual enzyme activity
30
how is MSUD inherited, and what is elevated?
autosomal recessive | Leu
31
what are the symptoms of MSUD
presents in first week of life poor feeding --> lethargy --> coma stroke, cerebral edema maple syrup smell
32
how do you diagnose MSUD
plasma AA show elevated BCAA and alloleucine
33
how do you treat acute MSUD
``` promote anabolic state stop Leu intake give Ile, Val IV dex/lipids prevent cerebral edema ```
34
how do you treat chronic MSUD
``` low Leu diet w/ formula supplement Ile, Val monitor BCAA illness -- reduce Leu intake liver transplant curative ```
35
how do organic acidemias present?
metabolic acidosis with ketosis and elevated anion gap
36
how do you diagnose organic acidemias?
metabolic acidosis with ketosis and elevated anion gap urine organic acids urine ketones secondary hyperammonemia in neonates from inhibition of urea cycle
37
How do you treat organic acidemias
low protein diet w/ formula carnitine supp. to bind organic acids relevant vitamin supp (i.e. biotin/B12) monitor ketones
38
how do you treat acidemias during acute decompensation
stop protein intake IV dex/lipids + insulin biocarbonate carnitine
39
how is propionic acidemia treated, what enzyme is defective, what is the metabolic defect?
autosomal recessive propionylCoa carboxylase defective defect in Val, Ile, Thr, Val, Met, odd chain FA metabolism
40
symptoms of propionic academia?
early onset encephalopathy = poor feeding --> lethargy, vomiting --> coma poor weight gain, chronic vomiting
41
propionic acidemia natural history?
recurrent episodes w/ fasting, illness, p intake illness = ketoacidosis, hyperammonemia late cardiomyopathy, movement disorder, stroke 80% mortality by adulthood
42
treatment for propionic academia?
low protein diet carnitine, biotin supp avoid fasting
43
what is the primary feature of urea cycle disorders?
hyperammonemia without acidosis
44
main symptom of urea cycle
poor feeding --> lethargy, vomiting --> coma
45
how do you approach an encephalopathic neonate/infant?
check ammonia!
46
what is diagnostic of urea cycle disorders?
plasma AA
47
What is the treatment for urea cycle disorders
``` limit protein intake special formula supp w/ arginine or citrulline give ammonia scavenger sick day management ```
48
how is OTC inherited, what is the enzyme deficiency, and what is elevated/low?
X linked ornithine transcarbamoylase low citrulline, elevated orotic acid
49
what is the natural history of OTC?
15% of females have severe hyperammonemia from random X inactivation in liver classically affected males die w/o liver transplant
50
how do you treat OTC?
``` major emergency: no protein intake glucose infusion IV arginine, sodium benzoate, sodium phenylacetate hemodialysis monitor cerebral edema ```
51
what is the primary feature of fatty acid oxidation?
hypoketotic hypoglycemia
52
at what age does FA ox disorder present?
once the age is reached when fasting is allowed (3-18 months)
53
what if FA ox disorder left untreated?
lethargy, coma, seizures, vomiting, SIDS
54
what are unique symptoms in long chain disorders?
cardiomyopathy and muscle weakness
55
how is FA ox disorder inherited?
AR
56
how do you diagnose FA ox disorder?
hypoketotic hypoglycemia elevated acylcarnitine urine organic acids
57
how do you treat FA ox
``` prevent hypoglycemia carnitine supp avoid fasts immunize cardiac eval ```
58
what is MCADD? primary feature?
medium acyl CoA dehydrogenase deficiency hypoketotic hypoglycemia

Clinical Genetics (6 decks)

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