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Example of facial characteristics of patient with Fragile X.
Example of facial characteristics of patient with Fragile X.
'''Educational Objective:'''  Fragile X syndrome is caused by expansion of CGG repeats in the FMR1 gene on the X Chromosome.
'''References:'''  First Aid 2012 page 92
|AnswerA=CAG
|AnswerA=CAG
|AnswerAExp=CAG repeats are seen in [[Huntington’s disease]].  '''Wiki-mnemomic:''' You hunt animals and put them in the '''CAG'''e: Huntington Disease '''CAG'''
|AnswerAExp=CAG repeats are seen in [[Huntington’s disease]].  '''Wiki-mnemomic:''' You hunt animals and put them in the '''CAG'''e: Huntington Disease '''CAG'''
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|AnswerE=CGG
|AnswerE=CGG
|AnswerEExp=CGG repeats are seen in [[Fragile X syndrome]]. The patient is suffering from [[mental retardation]] and enlarged face and jaw that are consistent with Fragile X syndrome.
|AnswerEExp=CGG repeats are seen in [[Fragile X syndrome]]. The patient is suffering from [[mental retardation]] and enlarged face and jaw that are consistent with Fragile X syndrome.
|EducationalObjectives=Fragile X syndrome is cause by repeat of the CGG trinucleotide repeat in the FMR1 gene.  It is the most common inherited cause of intellectual disability.
|EducationalObjectives=Fragile X syndrome is caused by expansion of CGG repeats in the FMR1 gene on the X Chromosome.  It is the most common inherited cause of intellectual disability.
|References=First Aid 2014 page 89
|References=First Aid 2014 page 89
|RightAnswer=E
|RightAnswer=E

Revision as of 18:30, 12 July 2014

 
Author [[PageAuthor::Rim Halaby, M.D. [1] (Edited by Will Gibson)]]
Exam Type ExamType::USMLE Step 1
Main Category MainCategory::Genetics
Sub Category SubCategory::General Principles
Prompt [[Prompt::A 17-year-old male is brought by his parents for an annual checkup with a new physician. The patient’s face and jaw appear to be larger than normal. The patient is slow in answering the physician's questions and sounds younger than his age. A review of his past medical history reveals cognitive assessments consistent with mental retardation. The patient’s condition is most likely caused by trinucleotide repeats of which of the following?]]
Answer A AnswerA::CAG
Answer A Explanation [[AnswerAExp::CAG repeats are seen in Huntington’s disease. Wiki-mnemomic: You hunt animals and put them in the CAGe: Huntington Disease CAG]]
Answer B AnswerB::GAA
Answer B Explanation [[AnswerBExp::GAA repeats are seen in Friedreich's ataxia.]]
Answer C AnswerC::GGA
Answer C Explanation AnswerCExp::GGA repeats are not specific to a disease.
Answer D AnswerD::CTG
Answer D Explanation [[AnswerDExp::CTG repeats are seen in myotonic dystrophy.]]
Answer E AnswerE::CGG
Answer E Explanation [[AnswerEExp::CGG repeats are seen in Fragile X syndrome. The patient is suffering from mental retardation and enlarged face and jaw that are consistent with Fragile X syndrome.]]
Right Answer RightAnswer::E
Explanation [[Explanation::The patient is suffering from mental retardation and enlarged face and jaw that are consistent with Fragile X syndrome. Fragile X syndrome is a syndrome of X-linked mental retardation. Boys with the syndrome may have large testicles (macroorchidism), prognathism, hypotonia and autism, and a characteristic but variable face with large ears, long face, high-arched palate, gynecomastia, and malocclusion. Additional abnormalities may include lordosis, heart defect, pectus excavatum, flat feet, shortening of the tubular bones of the hands, and joint laxity.

Fragile X syndrome is caused by a trinucleotide expansion of CGG repeats in the FMR1 gene on the X chromosome. Expansion of CGG repeats beyond a certain threshold causes silencing of the FMR1 gene thereby leading to pathology.

Example of facial characteristics of patient with Fragile X.
Educational Objective: Fragile X syndrome is caused by expansion of CGG repeats in the FMR1 gene on the X Chromosome. It is the most common inherited cause of intellectual disability.
References: First Aid 2014 page 89]]

Approved Approved::Yes
Keyword WBRKeyword::Mental retardation, WBRKeyword::Retardation, WBRKeyword::Repeat disorder, WBRKeyword::Nucleotide, WBRKeyword::Nucleotide repeat
Linked Question Linked::
Order in Linked Questions LinkedOrder::