WBR0143

Author	[[PageAuthor::Rim Halaby, M.D. [1]]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Genetics
Sub Category	SubCategory::General Principles
Prompt	[[Prompt::A 17-year-old male was brought by his parents for an annual checkup. The patient’s face and jaw appear to be larger than normal. The patient is slow in answering the physician's questions and sounded younger than his age. A review of his past medical history reveals documented decreased cognition level. 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.]]
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::GGG
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. Educational objective: Fragile X syndrome is caused by CGG repeats. Educational Objective: References: ]]
Approved	Approved::No
Keyword
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