WBR1018: Difference between revisions

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{{WBRQuestion
|QuestionAuthor={{Ochuko}}
|QuestionAuthor={{Ochuko}} (Reviewed by {{YD}})
|ExamType=USMLE Step 1
|ExamType=USMLE Step 1
|MainCategory=Biochemistry
|MainCategory=Biochemistry
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|MainCategory=Biochemistry
|MainCategory=Biochemistry
|SubCategory=General Principles
|SubCategory=General Principles
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|MainCategory=Biochemistry
|MainCategory=Biochemistry
|SubCategory=General Principles
|SubCategory=General Principles
|Prompt=A 5- month old boy was brought by the parents to the hospital with complaints of poor feeding and growth, hypotonia, lactic acidemia, and mild acidosis. The ratio of pyruvate to lactate in serum is elevated and there is decreased conversion of pyruvate to acetyl CoA in fibroblast. Which of the following compounds would most likely benefit this patient?
|Prompt=A 5-month-old boy was evaluated for poor feeding and growth, hypotonia, vomiting, lactic acidemia, and garlic breath. The ratio of pyruvate to lactate in the serum is elevated with decreased conversion of pyruvate to acetyl CoA in fibroblasts. Administration of the following compounds is recommended to manage this patient's condition?
|Explanation=An elevation of pyruvate and deficiency of acetyl CoA suggest a deficiency of pyruvate dehydrogenase, which requires thiamine (Vitamin B1), one of the cofactors in the pyruvate dehydrogenase complex. Findings include neurologic deficits, usually starting in infancy. Other cofactors include Vitamins B2 (Riboflavin or FAD+), B3 (Niacin or NAD+), B5 (CoA or Pantothenate) and Lipoic acid.
|Explanation=An elevation of pyruvate and deficiency of acetyl CoA suggest [[pyruvate dehydrogenase deficiency]], which typically manifests in infancy with neurologic deficits, poor feeding and growth, vomiting, hypotonia, lactic acidemia, rice water stools, and garlic breath. Administration of thiamine (vitamin B1) is usually recommended to manage patients with pyruvate dehydrogenase deficiency. Thiamine is a co-factor required for the normal functioning of the pyruvate dehydrogenase complex. Other co-factors include Vitamins B2 (Riboflavin or FAD+), B3 (Niacin or NAD+), B5 (CoA or Pantothenate), and lipoic acid.
MNEUMONIC: Tender Loving Care For Nancy (Thiamine, Lipoic acid, CoA, FAD+, NAD+).
 
 
Reference: First AID for the USMLE Step 1 2013 pgs 100-101
 
|AnswerA=Pyridoxine
|AnswerA=Pyridoxine
|AnswerAExp=Pyridoxine also known as vitamin B6 is not required in the pyruvate dehydrogenase complex. It is used in transamination (eg ALT and AST), decarboxylation reactions and glycogen phosphorylase.
|AnswerAExp=[[Pyridoxine]] (vitamin B6) is not a co-factor of the pyruvate dehydrogenase complex. Vitamin B6 is used in transamination (e.g. ALT and AST), decarboxylation reactions, and in glycogen phosphorylase.
|AnswerB=Thiamine
|AnswerB=Thiamine
|AnswerBExp=Correct. See explanation.
|AnswerBExp=[[Thiamine]] is a co-factor required for the normal functioning of the pyruvate dehydrogenase complex. Administration of thiamine (vitamin B1) is usually recommended to manage patients with pyruvate dehydrogenase deficiency.  
|AnswerC=Cobalamin
|AnswerC=Cobalamin
|AnswerCExp=Cobalamin, also known as Vitamin B12 is a cofactor for homocysteine methyltransferase and methylmalonyl-CoA mutase. It is not required in the pyruvate dehydrogenase complex.
|AnswerCExp=[[Cobalamin]] (vitamin B12) is a co-factor for homocysteine methyltransferase and methylmalonyl-CoA mutase. It is not a co-factor in the pyruvate dehydrogenase complex.
|AnswerD=Biotin
|AnswerD=Biotin
|AnswerDExp=Biotin is also known, as Vitamin B7 and it is a cofactor for carboxylation enzymes and not required in the pyruvate dehydrogenase complex.
|AnswerDExp=[[Biotin]] (vitamin B7) is a cofactor for carboxylation enzymes. It is not required in the pyruvate dehydrogenase complex.
|AnswerE=Ascorbic acid
|AnswerE=Ascorbic acid
|AnswerEExp=Ascorbic acid is also known as Vitamin C, necessary for hydroxylation of proline and lysine in collagen synthesis.
|AnswerEExp=[[Ascorbic acid]] (vitamin C) is necessary for the hydroxylation of proline and lysine during collagen synthesis.
|EducationalObjectives=Thiamine is a co-factor required for the normal functioning of the pyruvate dehydrogenase complex. Administration of thiamine (vitamin B1) is usually recommended to manage patients with pyruvate dehydrogenase deficiency.
|References=First Aid 2015 page 89, 99.
|RightAnswer=B
|RightAnswer=B
|WBRKeyword=Pyruvate dehydrogenase,  
|WBRKeyword=Pyruvate dehydrogenase, Vitamin B1, Thiamine, Neurologic deficit, Inborn error of metabolism, Pyruvate, Lactate, Acetyl-CoA
|Approved=Yes
|Approved=Yes
}}
}}

Revision as of 22:32, 16 August 2015
Author [[PageAuthor::Ogheneochuko Ajari, MB.BS, MS [1] (Reviewed by Yazan Daaboul, M.D.)]]
Exam Type ExamType::USMLE Step 1
Main Category MainCategory::Biochemistry
Sub Category SubCategory::General Principles
Prompt [[Prompt::A 5-month-old boy was evaluated for poor feeding and growth, hypotonia, vomiting, lactic acidemia, and garlic breath. The ratio of pyruvate to lactate in the serum is elevated with decreased conversion of pyruvate to acetyl CoA in fibroblasts. Administration of the following compounds is recommended to manage this patient's condition?]]
Answer A AnswerA::Pyridoxine
Answer A Explanation [[AnswerAExp::Pyridoxine (vitamin B6) is not a co-factor of the pyruvate dehydrogenase complex. Vitamin B6 is used in transamination (e.g. ALT and AST), decarboxylation reactions, and in glycogen phosphorylase.]]
Answer B AnswerB::Thiamine
Answer B Explanation [[AnswerBExp::Thiamine is a co-factor required for the normal functioning of the pyruvate dehydrogenase complex. Administration of thiamine (vitamin B1) is usually recommended to manage patients with pyruvate dehydrogenase deficiency.]]
Answer C AnswerC::Cobalamin
Answer C Explanation [[AnswerCExp::Cobalamin (vitamin B12) is a co-factor for homocysteine methyltransferase and methylmalonyl-CoA mutase. It is not a co-factor in the pyruvate dehydrogenase complex.]]
Answer D AnswerD::Biotin
Answer D Explanation [[AnswerDExp::Biotin (vitamin B7) is a cofactor for carboxylation enzymes. It is not required in the pyruvate dehydrogenase complex.]]
Answer E AnswerE::Ascorbic acid
Answer E Explanation [[AnswerEExp::Ascorbic acid (vitamin C) is necessary for the hydroxylation of proline and lysine during collagen synthesis.]]
Right Answer RightAnswer::B
Explanation [[Explanation::An elevation of pyruvate and deficiency of acetyl CoA suggest pyruvate dehydrogenase deficiency, which typically manifests in infancy with neurologic deficits, poor feeding and growth, vomiting, hypotonia, lactic acidemia, rice water stools, and garlic breath. Administration of thiamine (vitamin B1) is usually recommended to manage patients with pyruvate dehydrogenase deficiency. Thiamine is a co-factor required for the normal functioning of the pyruvate dehydrogenase complex. Other co-factors include Vitamins B2 (Riboflavin or FAD+), B3 (Niacin or NAD+), B5 (CoA or Pantothenate), and lipoic acid.

Educational Objective: Thiamine is a co-factor required for the normal functioning of the pyruvate dehydrogenase complex. Administration of thiamine (vitamin B1) is usually recommended to manage patients with pyruvate dehydrogenase deficiency.
References: First Aid 2015 page 89, 99.]]

Approved Approved::Yes
Keyword WBRKeyword::Pyruvate dehydrogenase, WBRKeyword::Vitamin B1, WBRKeyword::Thiamine, WBRKeyword::Neurologic deficit, WBRKeyword::Inborn error of metabolism, WBRKeyword::Pyruvate, WBRKeyword::Lactate, WBRKeyword::Acetyl-CoA
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