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biochem ii > 17 Inborn errors of metabolism > Flashcards

17 Inborn errors of metabolism Flashcards

1
Q

Why are genes for metabolic disorders usually mild?

A

proteins usually excess. Usually one gene needed

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2
Q

What are the biochemical characteristics of classical galactosemia?

A

Most common carb defect, galactose-1-phosphate uridyl trans affected, no galactose to glucose xvert, shunts to galactitol and galactonate

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3
Q

What are the symptoms of galactosemia?

A

Hepatic insufficiency, cataracts, development delay, mental retardation

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4
Q

What are prevention and Tx for galactosemia?

A

Blood enzyme screening and dietary restriction

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5
Q

What are the biochemical characteristics of hereditary fructose intolerance?

A

Defect in fru-1,6 bisphosphate leads to fructose intolerance and gas

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6
Q

What are the characteristics of Von Gierke Disease?

A

Glycogen storage disorder, defect glu6phos, glycogen is not metabolized/glu released from liver, hepatomegaly/hypoglycemia during starvation

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7
Q

What are the characteristics of phenylketonuria?

A

Defect in phenylalanine hydroxylase, no phenylalanine metabolism, accumulations disrupts brain =/= myelination, protein synth = retardation

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8
Q

What are the Tx and pregnancy factors for PKU?

A

Dietary limitations and high levels of phenylalanine can affect fetus

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9
Q

What are the characteristics of maple syrup urine disease?

A

Cannot metabolize BCAA, accumulation leads to neurodegeneration and death in one month

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10
Q

What is a special prevalence point in Maple syrup urine disease?

A

Usually rare but 1/7 for menonites

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11
Q

What are the characteristics of MCAD deficiency?

A

defect in MCAD, fatty acid defect, hypoglycemia after fasting, accumulates fatty acid intermediates = low ketone/glycogen = cerebral edema/death

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12
Q

What is Tx and prevention for MCAD deficiency?

A

Always have a supply of glucose, avoid fasting at all costs

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13
Q

What population is MCAD likely?

A

Northwest europeans

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14
Q

What is the most likely mutation in MCAD deficiency?

A

90% is single missense from A to G resulting in lysine to glutamate

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15
Q

What are the characteristics of congenital adrenal hyperplasia?

A

blocked corticosteroid synth in which excess androgenic precursors lead to virilization of females in-utero and salt-wasting(dehydration, lethargy)

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16
Q

What are the characteristics of Zellweger syndrome?

A

Peroxisome biogenesis disorder, neonatal hypotonia with distinctive face and death in infancy

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17
Q

What is the biochemical result of zellweger syndrome?

A

Does not allow the digestion of Very Long Chain Fatty acids and protein importing into the matrix

18
Q

What is the general molecular overview of lysosomal storage disorders?

A

Accumulation of nondegraded mucopolysaccharaides, sphingolipids, glycoproteins and glycolipids, most are enzyme defects that can inhibit transport or targeting

19
Q

What are the characteristics of mucopolysaccharidoses?

A

GAG degrade defect, sufate drugs inhibited, ten enzyme defects = six disorders, all autosomal recessive, but hunters = x linked recessive

20
Q

What are the similarities and differences of MPS?

A

chronic/multisystem = Hearing/vision/joint and cardiovascular problems may result. Mental retardation only in hurler, hunter and sanfilippo.

21
Q

How can hurler and scheie be differentiated?

A

Only clinically

22
Q

What are the three sphingolipidoses and their enzyme defects?

A

Gaucher - beta glucosidase, tay-sachs - beta hexosaminidase A, Niemann-Pick - sphingomyelinase

23
Q

What is a population consideration for gaucher?

A

Rare except in ashkenazi jews

24
Q

What are the characteristics of I-cell disease?

A

Phosphotransferase defect prevents mannose-6-p binding to proteins with lysosome targets = accumulated inclusions

25
Q

What are the four enzymes that can be affected in the urea cycle?

A

Carbamoyl phosphate synthetase (CPS). Ornithine transcarbamoylase (OTC). Arginosuccinate synthetase (ASA). Argininosuccinate (AS).

26
Q

What is the most common urea cycle defect and what type is it?

A

OTC deficiency an X-linked recessive gene

27
Q

What are the genetic and phenotypic characteristics of OTC deficiency?

A

10 exon can be mutated, females = symptomatic carriers, incr orotate/nitrogen (hyperammonemia)

28
Q

How is energy production phenotypes complex?

A

OXPHOS system as well as being able to use different substrates = many proteins and different requirements in different tissues = high complexity

29
Q

How can transport system phenotypes be simple?

A

Many transport systems but tissues may need similar substrates = same transporter in different tissues

30
Q

What are the characteristics of Cystinuria?

A

Common, 2 types, inability to transport cystine and dibasic amino acids causes accumulation = amino acid loss in urine, kidney stones

31
Q

What is cystine and what other amino acids are lost in cystinuria?

A

Cystine is 2 cysteines with a disulfide bond making it least soluble of all aa. Dibasic amino acids also include lysine, arginine and ornithine

32
Q

How can cystinuria kidney stones be Tx?

A

High pH and penicillamine will solubilize cystine

33
Q

What are the two genes mutated in cystinuria?

A

Type I - SLC3A1. Type II and III - SLC7A9

34
Q

What is another cystine associated genetic disorder?

A

Cystinosis in which transporter for lysosomes with cystine is defective. Leads to Fanconi syndrome

35
Q

What are the characteristics of wilson disease and what type of disorder is it?

A

Defect copper excretion.incr Cu in liver/ brain. dysarthria, arthropathy, cardiomyopathy, kidney/ liver damage. Kayser-Fleischer eye ring. metal ion xport disorder

36
Q

What are the genetic components of wilsons disease?

A

ATP7B gene. Expressed highly in liver/kidney. Many mutations known, 40% northern Europeans have only single missense

37
Q

What are the characteristics of Hereditary Hemochromatosis?

A

Excessive intestinal iron absorption. Accumulates in liver, heart, pancreas joints. Dx = liver biopsy w/ hemosiderin stain.

38
Q

What is the epidemiology of Hemochromatosis?

A

northern europeans 1/8 carrier. 1/200-400 affected. incomplete penetrance. symptoms 40yo male 40 female

39
Q

What are the genetic factors associated with hemochromatosis?

A

Mutation of C282Y of HFE gene. cysteine to tyrosine at beta 2 microglobulin domain. high prevalance = selective advantage?

40
Q

How is hemochromatosis Tx?

A

Reduce iron = phlebotomy (bleeding)

biochem ii (18 decks)

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