WBR0646: Difference between revisions

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|MainCategory=Biochemistry
|MainCategory=Biochemistry
|SubCategory=Dermatology, General Principles
|SubCategory=Dermatology, General Principles
|MainCategory=Biochemistry
|MainCategory=Biochemistry
|MainCategory=Biochemistry
|MainCategory=Biochemistry
|MainCategory=Biochemistry
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|MainCategory=Biochemistry
|MainCategory=Biochemistry
|SubCategory=Dermatology, General Principles
|SubCategory=Dermatology, General Principles
|Prompt=A 4 year old girl presents to the emergency room for 2 episodes of blood in the stools. History initially is inconclusive, but upon further questioning the mother explains that her child was recently diagnosed with a rare disorder that causes her to have very stretchy skin, and joints that can extend beyond the normal range. Considering this patient has a mutation in type 1 collagen, what co-factor is essential in the defective enzyme in this patient?
|Prompt=A 4-year-old girl presents to the emergency room for 2 episodes of blood in the stools. History is initially inconclusive, but further questioning reveals that the child was recently diagnosed with a rare disorder that causes her to have hyperelastic skin and hyperextensible joints. Considering this patient has a mutation in type 1 collagen, what co-factor is essential in the defective enzyme in this patient?
|Explanation=Ehlers-Danlos Syndrome is a rare inherited disease that is heterogeneous in presentation and pathologic mechanisms. Six subtypes of Ehlers-Danlos exist with each having distinct mutations affecting collagen synthesis. The classical types of Ehlers-Danlos involve mostly collagen type 1 and collagen type 4. One of the most studied pathological mechanisms of Ehlers-Danlos is a mutation affecting lysyl-oxidase, an enzyme responsible for collagen crosslinking in the extracellular matrix. Lysyl-oxidase requires copper as a cofactor to function effectively. Ehlers-Danlos classically presents with skin hyperextensibility, cutaneous fragility, joint hypermobility, and vascular anomalies.Mutations often involve the COL-A genes.
|Explanation=Ehlers-Danlos Syndrome is a rare inherited disease that is heterogeneous in presentation and pathologic mechanisms. Six subtypes of Ehlers-Danlos exist with each having distinct mutations affecting collagen synthesis. One of the most studied pathological mechanisms of Ehlers-Danlos is a mutation affecting lysyl-oxidase, an enzyme responsible for collagen crosslinking in the extracellular matrix. Lysyl-oxidase requires copper as a cofactor to function effectively. Ehlers-Danlos classically presents with skin hyperextensibility, cutaneous fragility, joint hypermobility, and vascular anomalies.




Learning objective: Ehlers-Danlos is a rare inherited disorder with certain forms characterized by defective corss-linking of collagen fibers due to abnormal lysyl-oxidase. Lysyl oxidase requires copper as a cofactor.
Reference:
Wenstrup RJ, Florer JB, Willing MC, et al. COL5A1 haploinsufficiency is a common molecular mechanism underlying the classical form of EDS. Am J Hum Genet. 2000;66(6):1766-76.
Mao JR, Bristow J. The Ehlers-Danlos syndrome: on beyond collagens. J Clin Invest. 2001;107(9):1063-9.
|AnswerA=Selenium
|AnswerA=Selenium
|AnswerAExp=Selenium is a known cofactor for thyroid hormone deiodinases. It has no function with lysyl-oxidase.
|AnswerAExp=Selenium is a known cofactor for thyroid hormone deiodinases. It has no function with lysyl-oxidase.
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|AnswerE=Biotin
|AnswerE=Biotin
|AnswerEExp=Biotin functions as a cofactor for carboxylation reactions (Acetyl-CoA carboxylase, methylcrotonyl-CoA carboxylase, and propionyl-CoA carboxylase). It has no function with lysyl-oxidase.
|AnswerEExp=Biotin functions as a cofactor for carboxylation reactions (Acetyl-CoA carboxylase, methylcrotonyl-CoA carboxylase, and propionyl-CoA carboxylase). It has no function with lysyl-oxidase.
|EducationalObjectives=Ehlers-Danlos is a rare inherited disorder with certain forms characterized by defective corss-linking of collagen fibers due to abnormal lysyl-oxidase. Lysyl oxidase requires copper as a cofactor.
|References=Wenstrup RJ, Florer JB, Willing MC, et al. COL5A1 haploinsufficiency is a common molecular mechanism underlying the classical form of EDS. Am J Hum Genet. 2000;66(6):1766-76.<br>
Mao JR, Bristow J. The Ehlers-Danlos syndrome: on beyond collagens. J Clin Invest. 2001;107(9):1063-9.
|RightAnswer=D
|RightAnswer=D
|WBRKeyword=Ehlers-Danlos Syndrome, Collagen sythesis, Lysyl oxidase, Copper
|WBRKeyword=Ehlers-Danlos Syndrome, Collagen sythesis, Lysyl oxidase, Copper,
|Approved=No
|Approved=Yes
}}
}}

Revision as of 16:06, 15 September 2014
Author [[PageAuthor::Rim Halaby, M.D. [1]]]
Exam Type ExamType::USMLE Step 1
Main Category MainCategory::Biochemistry
Sub Category SubCategory::Dermatology, SubCategory::General Principles
Prompt [[Prompt::A 4-year-old girl presents to the emergency room for 2 episodes of blood in the stools. History is initially inconclusive, but further questioning reveals that the child was recently diagnosed with a rare disorder that causes her to have hyperelastic skin and hyperextensible joints. Considering this patient has a mutation in type 1 collagen, what co-factor is essential in the defective enzyme in this patient?]]
Answer A AnswerA::Selenium
Answer A Explanation AnswerAExp::Selenium is a known cofactor for thyroid hormone deiodinases. It has no function with lysyl-oxidase.
Answer B AnswerB::Niacin
Answer B Explanation AnswerBExp::Niacin also known as vitamin B3 is an important cofactor for hydrogen transfer processes as NAD and NADP. It has no function with lysyl-oxidase.
Answer C AnswerC::Zinc
Answer C Explanation AnswerCExp::Zinc is very important in the formation of zinc fingers which constitute parts of some transcription factors. It has no function with lysyl-oxidase.
Answer D AnswerD::Copper
Answer D Explanation AnswerDExp::Copper is important for the proper functioning of lysyl-oxidase an enzyme defective in certain forms of Ehlers-Danlos syndrome.
Answer E AnswerE::Biotin
Answer E Explanation AnswerEExp::Biotin functions as a cofactor for carboxylation reactions (Acetyl-CoA carboxylase, methylcrotonyl-CoA carboxylase, and propionyl-CoA carboxylase). It has no function with lysyl-oxidase.
Right Answer RightAnswer::D
Explanation [[Explanation::Ehlers-Danlos Syndrome is a rare inherited disease that is heterogeneous in presentation and pathologic mechanisms. Six subtypes of Ehlers-Danlos exist with each having distinct mutations affecting collagen synthesis. One of the most studied pathological mechanisms of Ehlers-Danlos is a mutation affecting lysyl-oxidase, an enzyme responsible for collagen crosslinking in the extracellular matrix. Lysyl-oxidase requires copper as a cofactor to function effectively. Ehlers-Danlos classically presents with skin hyperextensibility, cutaneous fragility, joint hypermobility, and vascular anomalies.

Educational Objective: Ehlers-Danlos is a rare inherited disorder with certain forms characterized by defective corss-linking of collagen fibers due to abnormal lysyl-oxidase. Lysyl oxidase requires copper as a cofactor.
References: Wenstrup RJ, Florer JB, Willing MC, et al. COL5A1 haploinsufficiency is a common molecular mechanism underlying the classical form of EDS. Am J Hum Genet. 2000;66(6):1766-76.
Mao JR, Bristow J. The Ehlers-Danlos syndrome: on beyond collagens. J Clin Invest. 2001;107(9):1063-9.]]

Approved Approved::Yes
Keyword WBRKeyword::Ehlers-Danlos Syndrome, WBRKeyword::Collagen sythesis, WBRKeyword::Lysyl oxidase, WBRKeyword::Copper
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