WBR0123
| Author | [[PageAuthor::William J Gibson (reviewed by Rim Halaby, M.D. [1])]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Genetics |
| Sub Category | SubCategory::Neurology, SubCategory::General Principles |
| Prompt | [[Prompt::A 15 year old girl is brought into clinic for evaluation by a medical geneticist. As an infant she displayed significant development delays in both cognitive and motor functioning. She was only able to walk alone at the age of 32 months. Her gait now is wide-based and she has notable ataxia. She is severely mentally retarded, with a vocabulary of approximately 20 words. She has a history of tonic seizures, which are sometimes accompanied by fever. Despite these symptoms she has a pleasant demeanor and laughs often without humorous stimulus.]] |
| Answer A | AnswerA::Deletion of maternal allele; methylation of paternal allele on chromosome 14 |
| Answer A Explanation | [[AnswerAExp::Angelman syndrome is caused by deletion of the maternal allele and silencing of the paternal allele on chromosome 15.]] |
| Answer B | AnswerB::Deletion of paternal allele; methylation of maternal allele on chromosome 14 |
| Answer B Explanation | [[AnswerBExp::Angelman syndrome is caused by deletion of the maternal allele and silencing of the paternal allele on chromosome 15.]] |
| Answer C | AnswerC::Deletion of maternal allele; methylation of paternal allele on chromosome 15 |
| Answer C Explanation | [[AnswerCExp::Angelman syndrome is caused by deletion of the maternal allele and silencing of the paternal allele on chromosome 15.]] |
| Answer D | AnswerD::Deletion of paternal allele; methylation of maternal allele on chromosome 15 |
| Answer D Explanation | [[AnswerDExp::Angelman syndrome is caused by deletion of the maternal allele and silencing of the paternal allele on chromosome 15.]] |
| Answer E | AnswerE::Methylation of two maternal alleles on chromosome 15 |
| Answer E Explanation | [[AnswerEExp::Angelman syndrome is caused by deletion of the maternal allele and silencing of the paternal allele on chromosome 15.]] |
| Right Answer | RightAnswer::C |
| Explanation | [[Explanation::The patient in this vignette has Angelman syndrome. Angelman syndrome is a neuro-genetic disorder characterized by severe intellectual and developmental disability, sleep disturbance, seizures, jerky movements (especially hand-flapping), frequent laughter or smiling, and usually a happy demeanor. Angelman syndrome is caused by the deletion of the normal allele-specific expression of the maternal copy of several genes on chromosome 15 (imprinting).
Wiki-Mnemonic: Prader-Willi syndrome is due to deletion of the Paternal allele. AngelMan syndrome is due to deletion of the Maternal allele. |
| Approved | Approved::Yes |
| Keyword | WBRKeyword::Angelman syndrome, WBRKeyword::Genetics, WBRKeyword::Imprinting, WBRKeyword::Epigenetics |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |