rida
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What amino acid would you give to a child with PKU?
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| Bela
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Tyrosine!
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| mjl1717
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tyrosine becomes essential but phenyalanine IS essential but we give at very low levels monitoring blood levels. :idea:
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| rida
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:icon_salut:
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| Bela
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hey mjl, i didn't understand what u were trying to say. can u elaborate please?
what do u give at very low blood levels?
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| rida
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Bela what he is trying to say is that phenylalanine is an essential amino acid, so we need it in our diet, but if you have PKU, you are missing tyrosine hydroxylase, and PKU accumulates, and you have no tyrosine so tyrosine becomes an essential aa. These patients have to be kept on watch that their phenylalanine doesn't get outta control, hope it helps!!!
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| kalsam
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Good explanation..
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| Bela
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Right rida. So, giving pts Tyrosine is the correct answer?
What is Phenyalanine deletion associated with?
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| usmleasr
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cystic fibrosis 
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| Bela
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very good ace of usmle 
yup, deletion at the 408 position if I am not mistaken.
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| Alina T
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it's 508. close enough...
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| mjl1717
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Thx Rida--just want to say that the missing enzyme would be phenylalnine hydroxylase or a version of biopterin. [phenyalanine is given at very low levels]
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| Bela
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Ok guys, let's beat this to death since we haven't enough
What's the reason for a neonate to appear with signs and symptoms of PKU at birth? How about someone at week 2 of life?
What should the patients also eleminate in diet? I mean, what sbst is high in phenylalanine?
And mjl, I saw tetrahydrobiopterin in a test q. Didn't mention phenylalanine hydroxylase at all. So, I am glad u brought it up.
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| mash
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aspartame (an art. sweetener) should be avoided..........
woman with PKU with poor control during preg can hv a child with d ds at birth........
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| kalsam
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What's the reason for a neonate to appear with signs and symptoms of PKU at birth?
-Affected mother,without a phenylalanine free diet prior to conception
-hence fetus exposed to high level of phenylalanine will be born with profound mental retardation,seizures, extreme hyperactivity, and psychosis
Hence screening -Guthries'test
How about someone at week 2 of life?
-after birth they get exposed to milk containing phenylalanine.Hence they manifest with,
- Hypopigmentation-(Tyrosine is a substitute for melanin synthesis)
-Musty odor sweat ( is due to phenylalanine converted products via minor shunt pathway like phenylpyruvic acid,phenyllactic acid,phenylacetic acid..etc)
What should the patients also eleminate in diet? I mean, what sbst is high in phenylalanine?
Hmm..chewing gum :P
Foods rich in phenylalanine include almonds and peanuts; bananas and avocados; cheese and cottage cheese; lima beans; non-fat dried milk; pumpkin and sesame seeds; and pickled herring.
This information I googled it..
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| Bela
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very nice answer kalsam. I learned something new....about the gouthrie's test.
Yes, when the baby starts having the disease the second week, u must think of something genetic. Remember, pts with pku are usually normal @ birth!
Yes, pts should avoid foods containing ASPARTAME, a sweetener.
Another question I saw on Q bank but don't remember the choices as I haven't reviewed it yet.
***A couple goes to the GYN b/c the female is pregnant w/her 1st child. During the conversation, she mentions that she had PKU when young but was treated and hasn't had a problem ever since. What do you tell the couple in regards to the outcome of the baby?
Is he going to have PKU?
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| kalsam
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Look for mother's serum Phenylalanine level..
If it is more..then definitly fetus is going to have PKU, because it has already crossed the placenta..3rd to 8th week of gestation is the critical period...
Usually mothers with increased Phenylalanine level do good physically without any problems!!!
But how about normal mother with normal phenylalanine levels after the treatment????
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| rida
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"mjl1717" wrote:
Thx Rida--just want to say that the missing enzyme would be phenylalnine hydroxylase or a version of biopterin. [phenyalanine is given at very low levels]
Thanx mj for correcting me!!!!
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| mjl1717
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key points:
1)gene chromosome 12-spans 90kb of genomic DNA
2)many different versions of PKU
not only BH4 (tetrahydrobiopterin) but could be enzyme that
synthesizes or reduces this cofactor such as BH2 reductase
or BH2 synthetase BH4 also required for tyr. hydroxylase and
trp. hydroxylase
3)PKU has 40 or more mutations but in most populations the
majority of cases are caused by 6-10 mutaions
4)[extra]!--- tyrosine goes to tissue proteins, melanin,(probably res-
ponsible for fair hair,light skin) catecholamine, and fumarate
5)Neonate suspected with PKU do Guthrie test at birth and at 48
hrs. because initially you will probably get a false negative. Give
neonate a chance to digest milk, formula, protein.
6)Main item- keep phenylalanine levels LOW ( aspartimine too!)
7)[extra]!--these aromatic amino acids-trp.,tyr., phe are known as culprits
in liver disease and end stage liver disease. The a.a. amino acids enter
CNS and are converted to false neurotransmitters such as octopamine
and phenylethanolamine These false neurotransmitters are thought to
cause hepatic encephalopathy. The RX is more branched chain .a.a.
with low levels of aromatic amino acids. The branched chain a.a. inhibit
the aromatic a.a. from getting to CNS. This type mixture appears to
resolve hepatic encephalopathy quickly and the pt can tolerate larger
amounts of protein intake.
:idea:
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| rida
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thanx mjl!!!!
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