bluestar
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A 1-week-old newborn has had poor feeding, vomiting, and progressive lethargy over the past 4 days. She was born at term; pregnancy, labor, and delivery were uncomplicated, and she had no congenital anomalies. She is being breast-fed. She has a healthy 2-year-old brother; a sister died at 10 days of age after a full-term birth. Examination shows decreased muscle tone and poor responsiveness; reflexes are normal. Serum bicarbonate level is 8 mEq/L, pH is 7.15, and plasma ammonia level is 10 times the upper limit of normal. Which of the following is the most likely cause?
A ) Mitochondrial disorder
B) Mucopolysaccharidoses disorder
C ) Organic acid metabolism disorder
D) Renal tubular acidosis
E ) X-linked leukodystrophy
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| an
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c) organic acid metab ds
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| mixo
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C ) Organic acid metabolism disorder
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| bluestar
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which organic acid specifically?
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| warrofua
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Hey I'm new...
A 3rd year student at Virginia Tech studying Biochem. But enough introduction, I did some fairly extensive research (30 minutes  ) and couldn't come up with a definitive answer but have a guess.
Is it Argininosuccinic Acid?
*Edit - Figured I'd come back and back up my answer a bit.
I found that Argininosuccinic Aciduria (ASA) is a disorder of the urea cycle which prevents the patient from converting ammonia to urea. If we go further up the metabolic pathway, to the root of the problem...the enzyme argininosuccinic acid lyase is deficient in the patient so she cannot convert argininosuccinic acid to arginine. This condition could cause her to be Arginine deficient in addition to having the following symptoms: hyperammonemia, lack of appetite, vomiting, lethargy, seizures, and coma. Onset is usually at birth but symptoms may not be noticeable for a few days or weeks.
This disorder is obviously caused by a gene defect, both of her parents would be recessive carriers of ASA. The children of the carriers have a 25% chance of being born with the disease and a 50% chance of being a recessive carrier. This explains the healthy sibling of the family and the one who didn't make it.
This is an extremely rare disorder though (only 100 reported US cases), and the symptoms of the patient described in the question do not indicate she's had seizures (or coma  ) yet. Maybe a week days into diagnosis wasn't long enough to see all of the symptoms. Or maybe I overlooked a simpler, more common explanation. Whatever the result, it was fun! Good question!
Edited by warrofua on 10/07/05 - 03:22 PM. Reason: Backing Up Conclusion
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| allrad
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An elevated ammonium level without acidosis in a baby suggests a urea cycle defect.
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| sturge_weber
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please someone explain this question
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| LinaSarmiento
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but it does have acidosis...pH 7.15???????
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| Doc2378
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Well??? anyone'd like to try this one again.... ...I am lost!
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| Geroo
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i'm wondering why blustar didnt post the answer!!!
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