naperthrill
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A 2-year-old boy has brittle depigmented hair, cerebral atrophy, delayed myelination, motor delay, and mental retardation. Lysyl oxidase activity is decreased. The function of which of the following substances is most likely to be defective in this patient?
A) Albumin
B) Ceruloplasmin
C) Chondroitin sulfate
D) Collagen
What is the correct answer here????? I know that this is Menkes (Ehlos DAnlos type IX) where you have copper deficiency so your collagen synthesis is screwed up because of Decreased lysyl oxidase. However i cant decide between B or D. Ceruloplasmin being defective would lead to decreased copper transport but i know that collagen is defective also. Am i looking to deep into this question and is the answer just Collagen simply based on Menkes and Lysyl Oxidase. Any help is appreciated. Thanks!!!
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| drk1980
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lysyl oxidase activity is dec.....i think of just Collagen
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| Janka
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for sure it's D because of lysyl oxidase,
coeruloplasmin defects would show different symptoms (wilson's)
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| Geroo
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I go with B.it's menkes disease.answer D.is not specific
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| doc179
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yes in menkes its not the ceruloplasmin which is defective its the copper transport protein on the cell membrane which allows copper get out of the cell and then get attached to the carrier which is ceruloplasmin
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| Janka
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ok...you guys are right that the symptoms point to menkes. if coeruloplasmin was defective, we would have functional copper deficiency. lysyl oxidase activity then decreases secondarily...
but then, if doc179 is right (and i think he is) that in menkes it's not the coeruloplasmin which is defective, answer B cannot be right.
i go with D: if we have a functional copper deficiency (for whatever reason, doesn't matter), Lysyl oxidase activity decreases and we get deficient cross-linking of tropocollagen molecules and thus DEFECTIVE COLLAGEN --> ANSWER D
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| doc179
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yeah the ans is D collagen as the defective protein is not ceruloplasmin but the one which is on the cell membrane and hence once absorbed copper in the GI stays in the GI lining cells and is not available for collagen synthesis
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| naperthrill
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yes after some research everyone is correct. the answer is D collagen because its not ceruloplasmin but its the copper transport protein thats messed up. I guess this is one of those situations where if you know too much it can hurt you. Haha the lysyl oxidase and collagen just seemed TOO easy but i guess it was simpler than i had imagined.
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| SATELLITE
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hi
i'm glad that everyone agreed on D = collagen = Menke's disease. However, I wanted to know why would anyone even consider decrease in Ceruloplasmin. A decrease in Ceruloplasmin would mean that Total Copper Levels were decreased but it would not mean that there was a deficiency in the free copper.
Goljan's notes on Wilson's disease:
Total Copper Levels = Ceruloplasmin + Free Copper
IF ceruloplasmin is decreased, Total Copper Levels are Decreased.
Free Copper Levels are ELEVATED. The elevation of free copper levels depositing in brain, liver, and eye is what causes the symptoms of Wilson's : Kayser Eye, cirrhosis, lenticular nuclei degeneration.
Please clarify if my logic is incorrect or please explain your point with Ceruloplasmin.
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| amer_almohssen
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pathology of kinky hair disease is a mutation in the Xq gene ( the disease is X-linked recessive ) this mutation leads to a copper transporting ATPas defect---> decrease Cu absorption and transport----> collagen defect.
ceruloplasmin is a plasma globulin which carries Cu through out the body, it is decreased in Wilson's disease.
in wilsons disease the incorporation of Cu with ceruloplasmin, and the excretion of Cu into the bile is impaired, thus at the beginning of life Cu accumulates in the liver (causing hepatocyte pathology during the 1st decade) when Cu reaches a certain level, it starts to deposit in other body tissue, and cause toxicity to those cell organelles as well.
note ceruloplasmin is NEVER defective, but it is DECREASED in wilson's disease
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| yasmeen
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collagen is the correct answer
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| vamsi2004
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thanku satellite and amer for ur solid explanations.. goodluck.
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