WBR0369
| Author | [[PageAuthor::Serge Korjian, M.D., Gonzalo A. Romero, M.D. [1](Reviewed by Serge Korjian)]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Biochemistry, MainCategory::Pathology, MainCategory::Pathophysiology |
| Sub Category | SubCategory::Neurology |
| Prompt | [[Prompt::A research lab develops a new knock-in mouse model with a chimeric mouse/human exon containing 140 CAG repeats inserted into a gene located on the short arm of chromosome 4. The mice are grown and observed for 18 months. All mice develop increased locomotor activity and abnormal posturing around 1 month of age, followed by hypoactivity at 4 months and gait abnormalities at 1 year. Which of the following neurochemical changes is associated with this syndrome?]] |
| Answer A | AnswerA::Decreased norepinephrine, Decreased serotonin, Decreased dopamine |
| Answer A Explanation | [[AnswerAExp::These are the neurotransmitter changes associated in depression]] |
| Answer B | AnswerB::Increased norepinephrine, Increased serotonin, Increased dopamine |
| Answer B Explanation | [[AnswerBExp::This is seen in schizophrenia]] |
| Answer C | AnswerC::Increased acetylcholine, Increased serotonin, Decreased dopamine |
| Answer C Explanation | [[AnswerCExp::These changes are seen in parkinson’s disease]] |
| Answer D | AnswerD::Decreased GABA, Decreased acetylcholine, Increased dopamine |
| Answer D Explanation | AnswerDExp::These changes are associated with Huntington disease. |
| Answer E | AnswerE::Increased norepinephrine, Decreased GABA, Decreased serotonin |
| Answer E Explanation | [[AnswerEExp::These neurotransmitter changes are seen in anxiety]] |
| Right Answer | RightAnswer::D |
| Explanation | [[Explanation::The mouse model presented is an experimental approach for the investigation of Huntington's disease. The disorder has an autosomal dominant inheritance with the huntingtin gene on chromosome 4p harboring an expansion of the CAG repeats Educational Objective: Huntington's disease is an autosomal dominant disorder caused by a CAG trinucleotide expansion in the huntingtin gene on chromosome 4p. It is characterized by caudate atrophy leading to a decrease in GABA and acetylcholine, and an increase in dopamine. |
| Approved | Approved::Yes |
| Keyword | WBRKeyword::Huntington's disease, WBRKeyword::GABA, WBRKeyword::Serotonin, WBRKeyword::CAG, WBRKeyword::Trinucleotide repeat disorders, WBRKeyword::caudate |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |