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Old 08-28-2012
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Arrow Belindalimm Daily Questions: Biochemistry #4

A 4-year-old girl with a history of mental retardation is brought to the physician because of poor vision. Physical examination shows long limbs, tall stature, and kyphosis. Funduscopic examination shows bilateral lens dislocations. Laboratory studies are most likely to show a selective elevation of which of the following amino acids in serum?

A. Cystathionine
B. Cysteine
C. Methionine
D. Phenylalanine
E. Tyrosine
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Old 08-28-2012
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Methionine
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Old 08-28-2012
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Is it Marfan syndrome"?

Is it like Homocystinuria? so elevated

C. Methionine?

Confused
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Old 08-28-2012
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it's C) methionine

but methinonine is increased,if homocystinuria is caused by deficiency of cystathine synthase only....
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Old 08-29-2012
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Default C. Methionine

Marfan syndrome
As i remember arachydactyl is in homocystinuria and marfan.
So just co- relating that
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C...marfanoid habitus
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Default Answer is Methioine

The kid has long limbs, tall stature, all of which indicate Marfan-like habitus. And she also presents mental retardation. All of these symptoms give us a hint of homocystinuria, which results from cystathionine synthase deficiency. Because of the enzyme defect, homocysteine cannot be metabolized efficiently, and back up in blood. The accumulated homocysteine is alternatively metabolized to methionine by homocysteine methyl transferase and cofactor B12, assuming these is no defect in this metabolic pathway.
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Old 09-29-2012
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Quote:
Originally Posted by belindalimm View Post
The kid has long limbs, tall stature, all of which indicate Marfan-like habitus. And she also presents mental retardation. All of these symptoms give us a hint of homocystinuria, which results from cystathionine synthase deficiency. Because of the enzyme defect, homocysteine cannot be metabolized efficiently, and back up in blood. The accumulated homocysteine is alternatively metabolized to methionine by homocysteine methyl transferase and cofactor B12, assuming these is no defect in this metabolic pathway.
dear belinda........please tell me that how we r going to differentiate between homocystinuria methyl transferase def. and cystathionine def.....??????baed on this ques....
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Old 09-30-2012
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Quote:
Originally Posted by eshaan View Post
dear belinda........please tell me that how we r going to differentiate between homocystinuria methyl transferase def. and cystathionine def.....??????baed on this ques....

here is no option of fibrilin or marfan syndrome,question is about which amino acid is elevated and with marfans syndrome lens dislocation ocurs in outward and upwrd direction while with homocystinuria lens dislocation ocurs in down and inward direction.

inheritance:
Marfan's - autosomal dominant
homocystinuria - autosomal recessive

aortic incompetence:
Marfan's - aortic incompetence may occur
homocystinuria - heart rarely affected,, atherosclerosis seen
intellectual development:
Marfan's - normal
homocystinuria - mental retardation
other principle features:
Marfan's - flat feet, herniae, scoliosis; there is a 50% reduction in life expectancy
homocystinuria - osteoporosis, recurrent thromboembolism; characteristic laboratory features - plasma methionine and homocystine levels are elevated, homocystine is excreted in the urine, plasma cystine levels are reduced, positive urine cyanide-nitroprusside test; response to treatment with pyridoxine
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Old 09-30-2012
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Quote:
Originally Posted by riya rai View Post
here is no option of fibrilin or marfan syndrome,question is about which amino acid is elevated and with marfans syndrome lens dislocation ocurs in outward and upwrd direction while with homocystinuria lens dislocation ocurs in down and inward direction.

inheritance:
Marfan's - autosomal dominant
homocystinuria - autosomal recessive

aortic incompetence:
Marfan's - aortic incompetence may occur
homocystinuria - heart rarely affected,, atherosclerosis seen
intellectual development:
Marfan's - normal
homocystinuria - mental retardation
other principle features:
Marfan's - flat feet, herniae, scoliosis; there is a 50% reduction in life expectancy
homocystinuria - osteoporosis, recurrent thromboembolism; characteristic laboratory features - plasma methionine and homocystine levels are elevated, homocystine is excreted in the urine, plasma cystine levels are reduced, positive urine cyanide-nitroprusside test; response to treatment with pyridoxine
ya the question asked about amino acid elevation.....but eshaan asked about the differentiation b/w HMT def and cystathione synthase def...?
i also have the same doubt....if in HMT deficiency no methionine increase is seen.....only in cystathione synthase def. methionine increase is seen..(anyways options will provide us answer i guess)
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Quote:
Originally Posted by venky2600 View Post
ya the question asked about amino acid elevation.....but eshaan asked about the differentiation b/w HMT def and cystathione synthase def...?
i also have the same doubt....if in HMT deficiency no methionine increase is seen.....only in cystathione synthase def. methionine increase is seen..(anyways options will provide us answer i guess)
ya ehsan is asking about that i did mistake in reading his question thanks for corecting mine mistake,ya you are saying right that we have to understand what question is asking about,clues wil be there in question acording to me i have no more idea about it.
anyway best of luck,
am so woried i havnt started uworld in next two months is mine exame and still am doing goljan audio lecture but before uworld i would like to go thru first aid,here am double minded should i start uworld now or before that should i complete first aid?

Last edited by riya rai; 09-30-2012 at 10:08 AM.
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