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Thread: #23 Jordan

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    IMG SURVIVOR's Avatar
    IMG SURVIVOR is offline Moderator 536 points
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    #23 Jordan

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    What aminoacids will be deficient in a patient with homocystinuria?




















    CYSTEIN
    ORNITHINE
    LYSINE
    ARGININE
    Moderator: USMLE AND Residency Forums.

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    why even bother with the obvious. Just know where you are need it and where you can help the most.

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    md90's Avatar
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    can also be r/t methionine synthase deficiency where it catalyzes from homocysteine to Methionine

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    st_55 is offline Member 510 points
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    hi

    hey guys..correct me if i am wrong..but with homocystinuria..you have an elevation in cysteine and decrease in methionine due to the defiency in methionine synthase.

    cystinuria is the inherited defect where there is a renal tubular defect and you have elevated levels of cysteine, ornithine, lysine and arginine...people with this defect are predisposed to having kidney stones.

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    IMG SURVIVOR's Avatar
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    Bump this thread
    Moderator: USMLE AND Residency Forums.

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    why even bother with the obvious. Just know where you are need it and where you can help the most.

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    drhardy is offline Junior Member 510 points
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    I just remember COAL for this

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    IMG SURVIVOR's Avatar
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    Quote Originally Posted by drhardy View Post
    I just remember COAL for this
    COLA for me
    Moderator: USMLE AND Residency Forums.

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    why even bother with the obvious. Just know where you are need it and where you can help the most.

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    cooolguy is offline Member 49 points
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    I think that st_55 is correct for this thread. There are two conditions, homocystinuria and cystinuria

    Cystinuria refers to the failure of reabsorption of the COAL amino acids in the kidneys and somewhat in the small intestine (because they use the same transporters). The main amino acid to be concerned with is cysteine because it can precipitate and form kidney stones under high concentrations

    whereas

    Homocystinuria is the metabolic disorder which is caused by defective methionine breakdown due to the faulty enzyme cystathione (beta) synthase. This results in cardiovascular problems similar to Marfan's and a characteristic dislocation of the lens.

    Hope it helps

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    aya
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    homocystinuria is an inborn error of cystathionine synthase enzyme.
    thus, homocysteine can not combine with serine to form cystathionine, (and further cysteine and homoserine), so homocysteine accumulates in large amounts and becomes converted into homocystine that is in turn excreted in huge amounts in urine.

    serum homocysteine and methionine levels are ELEVATED

    THE DEFICIENT AMINO ACID IN THIS DISEASE IS CYSTEINE,
    which becomes then an essential one, although it is not in normal subjects.

    the disease has some common symptoms with marfan's syndrome, yeah that's correct

    it is treated by feeding a diet low in methionine high in cysteine.

    in cystinuria,or cystine-lysinuria, things are totally different.
    the defect is renal not enzymatic.
    the defect is in the transporter for the reabsorption of the diamino acids (Cystine, Ornithine, Lysine,Arginine). cystine concentration in urine is elevated and it precipitates forming UT stones

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