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KCSU17 Genetics > amino acid disorders + urea cycle disorders + lipid disorders > Flashcards

amino acid disorders + urea cycle disorders + lipid disorders Flashcards

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1
Q

amino acid disorders discussed in this class

A

phenylketonuria (PKU)

maple syrup urine disease (MUSD)

alkaptonuria

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2
Q

PKU inheritance + general

A

autosomal recessive

impaired ability to metabolize phenylalanine

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3
Q

PKU genetic abnormality

A

mutations involving loci encoding for PAH on chromosome 12q

mutations include substitutions, insertions, deletions

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4
Q

PKU

enzyme affected

A

phenylalanine hydroxylase (PAH)

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5
Q

PKU

effect on substrate/byproduct

A

buildup of phenylalanine

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6
Q

PKU

pathophys

A

elevated levels of plasma phenylalanine that disrupts essentail cellular proccesses in the brain and eventually causes mental retardation

PKU levels of phenylalanine are 6-80 mg/dl (normal is 1 mg/dl)

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7
Q

PKU

clinical manifestations

A

untreated PKU has severe mental retardation

normal at birth then progressive developmetnaly delay

must catch early and control

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8
Q

PKU

expression/penetrance

A

disease freq. varies by population

turkey has high incidence rate

high in yeminite jewish populaiton, northern/eastern europe, italy, and china

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9
Q

PKU treatment

A

restoring normal blood phe levels thru restricting dietary phe

strong relationship exists between control of blood phe levels in childhood and IQ

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10
Q

rare autosomal recessive diorder that involves defects in catabolic pathway of branched chain amino acids

A

maple syrup urine disease

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11
Q

MUSD

genetic abnormality

A

caused by mutaiton of 1 of 6 loci that envode for the branched chain amino acid complex (BCKAD complex)

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12
Q

BCKAD complex

A

composed of 4 catalytic components and 2 regulatory enzymes

most mutations occur in the catalytic compenent section

normally involved in decarboxylation of alpha keto acids of branched chain AAs to their acyl-CoA

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13
Q

MUSD

enzyme affected

A

BCKAD Complex

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14
Q

branched chain amino acids

A

leucine, isoleucine, valine

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15
Q

effect on substrate/byproduct

MUSD

A

accumulation of branched chain amino acids (valine, leucine, isoleucine)

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16
Q

leucine accumulation

A

neurological symptoms bc it is transported rapidly across BBB and metabolized to yield presumably glutamate and glutamine

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17
Q

elevation of plasma isoleucine…

A

maple syrup odor of urine

18
Q

clinical manifestation of MSUD

A

accumulation of any of the 3 AA leads to encephalopathy and progressive neurodegeneration in infants not treated

poor feeding, vomiting, failure to thrive, increased lethargy

19
Q

MSUD expression and prevalance

A

more prevalant in populations with high frequency of consanguinity

ex. mennonite community of Lancaster County, PA

symptoms devleop in neonates aged 4-7 days

variability

20
Q

MSUD

treatment

A

early diagnosis and diet intervention to prevent complications and allow normal IQ

dietary restriction of branched chain AAs to only what is minimally needed

thiamine supplement

21
Q

Alkapotnuria

Genetic abnormality

A

HGO gene

defect in catabolic pathway of tyrosine

22
Q

intermediate product of tyrosine catabolic pathway

A

homogentisic acid

23
Q

Alkapotnuria

enzyme affected

A

deficiency of HGO

24
Q

Alkapotnuria

effect on substrate/byproduct

A

deficiency of HGO causes accumulation of homogentisic acid

homogentisic acid is rapidly cleared in kidney and excreted

25
Q

Alkapotnuria

A

Plasma homogentisic acid is originally low due to rapid kidney clearence

however w/time it is depostited in cartilage throughout the body resulting in a build up of dark pigment (onchronosis)

normally transparent tissues will become slate blue

26
Q

Alkaptonuria

clincial manifestations

A

upon contact with open air, homogentisic acid is ozidized to form a pigment like polymeric material

causes the black color of standing urine

by 4th decade, tissues are slate blue

arthritis (spine, lrg joints)

27
Q

Alkaptonuria

expression

A

HGO shows a wide spectrum of mutation with high variability

28
Q

Alkaptonuria

treatment

A

redution of Phe and Tyr reduces homogentisic acid excretion

vitamin C supplement for older children and adults to reduce cartilage deposits

29
Q

urea cycle disorder discussed in this class

A

orinthine transcarbamylase deficiency

30
Q

orinthine transcarbamylase deficiency

inheritance

A

X linked disorder

(mostly in males, not females bc of X-inactivation)

31
Q

orinthine transcarbamylase deficiency

enzyme

A

orinthine transcarbamylase deficiency

used in urea cycle to detoxify and excrete nitrogen

32
Q

orinthine transcarbamylase deficiency

clincial manifestations

A

excess nitrogen causing severe hyperammonemia in neonate (24-48 hrs after ingesting protein)

progressive lethargy and decreased levels of conciousness Ias nitrogen levels increase)

symptomatic females may displat headache or vomiting after consuming high protein meals and learning diabilities

33
Q

orinthine transcarbamylase deficiency

expression/penetrance

A

primary affects males

females be symptomatic

34
Q

orinthine transcarbamylase deficiency

treatment

A

early, aggresive

IV fluid, glucose, benzoic acid, penylacetate

high risk of recurrent hyperammonemia

35
Q

lipid disorder discussed in this class

A

medium chain acyl-CoA Dehydrogenase (MCAD)

36
Q

most common fatty acid metabolic disorder

A

medium chain acyl-CoA dehydrogenase (MCAD)

37
Q

MCAD genetic abnormality

A

results from deficiency of medium chain acyl-coenzyme A dehydrogenase

38
Q

enzyme affected

MCAD

A

medium chain -acyl coenzyme A dehydrogenase

39
Q

MCAD

effect on substrate/byproduct

A

fasting results in accumulation of fatty acid intermediates and exhausts gluclose supply

40
Q

MCAD

clinicla manifestations

A

episodic hypoglycemia often provoked by fasting

may have vomiting and lethargy following fasting in children

cerebal edema and encephalopathy

41
Q

MCAD treatment

A

support during times of nutritional stress

eat enough calories and avoid fasting

KCSU17 Genetics (14 decks)

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