WBR0988: Difference between revisions

Jump to navigation Jump to search
VisualWikitext
No edit summary
No edit summary
Line 1: Line 1:
{{WBRQuestion
{{WBRQuestion
|QuestionAuthor={{Rim}}
|QuestionAuthor={{YD}} (Reviewed by {{YD}})
|ExamType=USMLE Step 1
|ExamType=USMLE Step 1
|MainCategory=Biochemistry
|MainCategory=Biochemistry
Line 21: Line 21:
|MainCategory=Biochemistry
|MainCategory=Biochemistry
|SubCategory=General Principles
|SubCategory=General Principles
|Prompt=A 25 year old male presents to the emergency department for acute chest pain radiating to the left arm and associated with nausea and sweating.  EKG reveals ST elevation in the anterior leads and the troponin level is elevated. The patient was admitted to the cath laboratory and appropriate management was initiated. Further investigations reveal an elevated level of homocysteine and methionine in the blood and urine. Supplementation with which of the following vitamins could possibly improve the condition of this patient?
|Prompt=A 25-year-old man presents to the emergency department (ED) with acute chest pain radiating to the left arm. He states that his pain is associated with nausea and cold sweating.  In the ED, ECG is remarkable for ST-segment elevation in the anterior leads, and the serum troponin concentration is elevated. The patient is transferred to the catheterization laboratory for urgent percutaneous coronary intervention (PCI). The next day, further investigations are remarkable for elevated concentrations of homocysteine and methionine in the blood and urine. Supplementation with which of the following vitamins could possibly improve this patient's condition?
|Explanation=Classic [[homocystinuria]] is an autosomal recessive disorder of [[methionine]] metabolism.  The amino acid methione is usually converted to homocysteine during its degradation. In homocystinuria, this process is impaired. Homocystinuria is characterized by an accumulation of [[homocysteine]] in the serum and an increased excretion of homocysteine in the urine.  It is associated with thromboembolic events at an early age, as seen in this patient, as well as with [[myopia]], [[ectopia lentis]] and [[marfanoid feature]]s. Mild cases of classic homocystinuria are responsive to [[pyridoxine]] (vitamin B6) supplementation.
|Explanation=Classic [[homocystinuria]] is an autosomal recessive disorder characterized by impaired [[methionine]] metabolism.  The amino acid methione is normally converted to homocysteine during its degradation. In homocystinuria, this process is impaired. Homocystinuria is characterized by an accumulation of [[homocysteine]] in the serum and an increased excretion of homocysteine in the urine.  It is associated with thromboembolic events at an early age, early [[myopia]], [[ectopia lentis]] and [[marfanoid feature]]s. Mild cases of classic homocystinuria are responsive to [[pyridoxine]] (vitamin B6) supplementation.
 
|AnswerA=Pyridoxine
|AnswerA=Pyridoxine
|AnswerAExp=[[Pyridoxine]] (vitamin B6) might increase the activity of the enzyme [[cystathionine synthase]] in mild pyridoxine cases of [[homocystinuria]].
|AnswerAExp=[[Pyridoxine]] (vitamin B6) may increase the activity of the enzyme [[cystathionine synthase]] in mild cases of [[homocystinuria]].
|AnswerB=Thiamine
|AnswerB=Thiamine
|AnswerBExp=[[Pyridoxine]] (vitamin B6), and not [[thiamine]] (vitamin B1), might increase the activity of the enzyme [[cystathionine synthase]] in mild pyridoxine cases of [[homocystinuria]].
|AnswerBExp=[[Thiamine]] (vitamin B1) supplementation is indicated in [[Wernicke-Korsakoff syndrome]] and [[beriberi]].
|AnswerC=Biotin
|AnswerC=Biotin
|AnswerCExp=[[Pyridoxine]] (vitamin B6), and not [[biotin]] (vitamin B7), might increase the activity of the enzyme [[cystathionine synthase]] in mild pyridoxine cases of [[homocystinuria]].
|AnswerCExp=[[Biotin]] (vitamin B7) supplementation is indicated in biotin deficiency.
|AnswerD=Folic acid
|AnswerD=Folate
|AnswerDExp=[[Pyridoxine]] (vitamin B9), and not [[folic acid]] (vitamin B1), might increase the activity of the enzyme [[cystathionine synthase]] in mild pyridoxine cases of [[homocystinuria]].
|AnswerDExp=[[Folate]] (vitamin B9) supplementation is indicated among pregnant women and patients with megaloblastic anemia due to folate deficiency.
|AnswerE=Riboflavin
|AnswerE=Riboflavin
|AnswerEExp=[[Pyridoxine]] (vitamin B6), and not [[riboflavin]] (vitamin B2), might increase the activity of the enzyme [[cystathionine synthase]] in mild pyridoxine cases of [[homocystinuria]].
|AnswerEExp=[[Riboflavin]] (vitamin B2) supplementation is indicated in cheilosis (vitamin B2 deficiency).
|EducationalObjectives=Classical [[homocystinuria]] is an autosomal recessive disorder of the metabolism of the amino acid [[methionine]]. Mild cases of classic homocystinuria are responsive to [[pyridoxine]] (vitamin B6) supplementation.
|EducationalObjectives=Classical [[homocystinuria]] is an autosomal recessive disorder characterized by impaired methionine metabolism. Mild cases of classic homocystinuria are responsive to [[pyridoxine]] (vitamin B6) supplementation.
|References=Reish, O., Townsend, D., Berry, S. A., Tsai, M. Y., King, R. A. Tyrosinase inhibition due to interaction of homocyst(e)ine with copper: the mechanism for reversible hypopigmentation in homocystinuria due to cystathionine beta-synthase deficiency. Am. J. Hum. Genet. 57: 127-132, 1995.<br>
|References=Reish O, Townsend D, Berry SA, et al. Tyrosinase inhibition due to interaction of homocyst(e)ine with copper: the mechanism for reversible hypopigmentation in homocystinuria due to cystathionine beta-synthase deficiency. Am J Hum Genet. 1995;57:127-132.<br>
First Aid 2015 page 108
First Aid 2015 page 108.
|RightAnswer=A
|RightAnswer=A
|WBRKeyword=Homocystinuria, Pyridoxine, Metabolism, Biochemistry, Genetics, Vitamins, Nutrition, Amino acids.
|WBRKeyword=Homocystinuria, Pyridoxine, Metabolism, Biochemistry, Genetics, Vitamins, Nutrition, Amino acids, Myocardial infarction, STEMI
|Approved=Yes
|Approved=Yes
}}
}}

Revision as of 23:14, 15 August 2015
Author [[PageAuthor::Yazan Daaboul, M.D. (Reviewed by Yazan Daaboul, M.D.)]]
Exam Type ExamType::USMLE Step 1
Main Category MainCategory::Biochemistry
Sub Category SubCategory::General Principles
Prompt [[Prompt::A 25-year-old man presents to the emergency department (ED) with acute chest pain radiating to the left arm. He states that his pain is associated with nausea and cold sweating. In the ED, ECG is remarkable for ST-segment elevation in the anterior leads, and the serum troponin concentration is elevated. The patient is transferred to the catheterization laboratory for urgent percutaneous coronary intervention (PCI). The next day, further investigations are remarkable for elevated concentrations of homocysteine and methionine in the blood and urine. Supplementation with which of the following vitamins could possibly improve this patient's condition?]]
Answer A AnswerA::Pyridoxine
Answer A Explanation [[AnswerAExp::Pyridoxine (vitamin B6) may increase the activity of the enzyme cystathionine synthase in mild cases of homocystinuria.]]
Answer B AnswerB::Thiamine
Answer B Explanation [[AnswerBExp::Thiamine (vitamin B1) supplementation is indicated in Wernicke-Korsakoff syndrome and beriberi.]]
Answer C AnswerC::Biotin
Answer C Explanation [[AnswerCExp::Biotin (vitamin B7) supplementation is indicated in biotin deficiency.]]
Answer D AnswerD::Folate
Answer D Explanation [[AnswerDExp::Folate (vitamin B9) supplementation is indicated among pregnant women and patients with megaloblastic anemia due to folate deficiency.]]
Answer E AnswerE::Riboflavin
Answer E Explanation [[AnswerEExp::Riboflavin (vitamin B2) supplementation is indicated in cheilosis (vitamin B2 deficiency).]]
Right Answer RightAnswer::A
Explanation [[Explanation::Classic homocystinuria is an autosomal recessive disorder characterized by impaired methionine metabolism. The amino acid methione is normally converted to homocysteine during its degradation. In homocystinuria, this process is impaired. Homocystinuria is characterized by an accumulation of homocysteine in the serum and an increased excretion of homocysteine in the urine. It is associated with thromboembolic events at an early age, early myopia, ectopia lentis and marfanoid features. Mild cases of classic homocystinuria are responsive to pyridoxine (vitamin B6) supplementation.

Educational Objective: Classical homocystinuria is an autosomal recessive disorder characterized by impaired methionine metabolism. Mild cases of classic homocystinuria are responsive to pyridoxine (vitamin B6) supplementation.
References: Reish O, Townsend D, Berry SA, et al. Tyrosinase inhibition due to interaction of homocyst(e)ine with copper: the mechanism for reversible hypopigmentation in homocystinuria due to cystathionine beta-synthase deficiency. Am J Hum Genet. 1995;57:127-132.
First Aid 2015 page 108.]]

Approved Approved::Yes
Keyword WBRKeyword::Homocystinuria, WBRKeyword::Pyridoxine, WBRKeyword::Metabolism, WBRKeyword::Biochemistry, WBRKeyword::Genetics, WBRKeyword::Vitamins, WBRKeyword::Nutrition, WBRKeyword::Amino acids, WBRKeyword::Myocardial infarction, WBRKeyword::STEMI
Linked Question Linked::
Order in Linked Questions LinkedOrder::
Retrieved from "https://www.wikidoc.org/index.php?title=WBR0988&oldid=1132679"