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 presented to the clinic for an annual checkup. This is the first time you see the patient. The patient’s face and jaw appear to be larger than normal. As you are asking him questions, you notice that the patient is slow in answering 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. |
| Approved | Approved::No |
| Keyword | |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |