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{{WBRQuestion
{{WBRQuestion
|QuestionAuthor=William J Gibson (reviewed by {{Rim}})
|QuestionAuthor=William J Gibson (reviewed by {{YD}})
|ExamType=USMLE Step 1
|ExamType=USMLE Step 1
|MainCategory=Genetics
|MainCategory=Genetics
Line 21: Line 21:
|MainCategory=Genetics
|MainCategory=Genetics
|SubCategory=Neurology, General Principles
|SubCategory=Neurology, General Principles
|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.
|Prompt=A 15-year-old girl is brought 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 past medical history is also significant for tonic seizures. Today, her gait is wide-based and she has notable ataxia. She is severely mentally retarded, with a vocabulary of approximately 20 words. Despite these symptoms she has a pleasant demeanor and laughs often without humorous stimulus.
|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, [[seizure]]s, 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]]).
|Explanation=[[Angelman syndrome]] (AS), also known as the "happy puppet" syndrome, is a neurodevelopmental disorder characterized by severe intellectual and developmental disability, sleep disturbance, [[seizure]]s, jerky movements (especially hand-flapping), frequent laughter or smiling, love of water, and usually a happy demeanor. Prominent facial features also include protruding jaw and tongue, deep set eyes, wide mouth, and flat occiput with microcephaly.  


'''Wiki-Mnemonic:''' '''P'''rader-Willi syndrome is due to deletion of the '''P'''aternal allele. Angel'''M'''an syndrome is due to deletion of the '''M'''aternal allele.
[[Angelman syndrome]] is most commonly caused by a deletions of in genes of maternal-derived alleles of chromosome 15. Other causes of AS include uniparental disomy for chromsome 15, imprinting (methylation) defect, and mutations within the gene that encode ubiquitin protein ligase (UBE3A).
|AnswerA=Deletion of maternal allele; methylation of paternal allele on chromosome 14
 
|AnswerAExp=[[Angelman syndrome]] is caused by deletion of the maternal allele and silencing of the paternal allele on chromosome 15.
|AnswerA=Deletion of a maternal-derived allele; methylation of a paternal-derived allele on chromosome 14
|AnswerB=Deletion of paternal allele; methylation of maternal allele on chromosome 14
|AnswerAExp=[[Angelman syndrome]] is caused by deletion of the maternal-derived allele and silencing of the paternal-derived allele on chromosome 15.
|AnswerBExp=[[Angelman syndrome]] is caused by deletion of the maternal allele and silencing of the paternal allele on chromosome 15.
|AnswerB=Deletion of paternal-derived allele; methylation of maternal-derived allele on chromosome 14
|AnswerC=Deletion of maternal allele; methylation of paternal allele on chromosome 15
|AnswerBExp=[[Angelman syndrome]] is caused by deletion of the maternal-derived allele and silencing of the paternal-derived allele on chromosome 15.
|AnswerCExp=[[Angelman syndrome]] is caused by deletion of the maternal allele and silencing of the paternal allele on chromosome 15.
|AnswerC=Deletion of maternal-derived allele; methylation of paternal-derived allele on chromosome 15
|AnswerD=Deletion of paternal allele; methylation of maternal allele on chromosome 15
|AnswerCExp=[[Angelman syndrome]] is caused by deletion of the maternal-derived allele and silencing of the paternal-derived allele on chromosome 15.
|AnswerDExp=[[Angelman syndrome]] is caused by deletion of the maternal allele and silencing of the paternal allele on chromosome 15.
|AnswerD=Deletion of paternal-derived allele; methylation of maternal-derived allele on chromosome 15
|AnswerE=Methylation of two maternal alleles on chromosome 15
|AnswerDExp=[[Angelman syndrome]] is caused by deletion of the maternal-derived allele and silencing of the paternal-derived allele on chromosome 15.
|AnswerEExp=[[Angelman syndrome]] is caused by deletion of the maternal allele and silencing of the paternal allele on chromosome 15.
|AnswerE=Methylation of two maternal-derived alleles on chromosome 15
|EducationalObjectives=Angelman syndrome is caused by deletion of the normally imprinted maternal allele on chromosome 15.
|AnswerEExp=[[Angelman syndrome]] is caused by deletion of the maternal-derived allele and silencing of the paternal-derived allele on chromosome 15.
|References=First Aid 2104 page 85; First Aid 2012 page 88.
|EducationalObjectives=Angelman syndrome is caused by deletion of the normally imprinted maternal-derived allele on chromosome 15.
|References=Clayton-Smith J, Laan L. Angelman syndrome: a review of the clinical and genetic aspects. J Med Genet. 2003;40:87-95.<br>First Aid 2104 page 85
|RightAnswer=C
|RightAnswer=C
|WBRKeyword=Angelman syndrome, Genetics, Imprinting, Epigenetics
|WBRKeyword=Angelman syndrome, Genetics, Imprinting, Epigenetics, Chromosome 15
|Approved=Yes
|Approved=Yes
}}
}}

Revision as of 15:23, 7 October 2014
Author [[PageAuthor::William J Gibson (reviewed by Yazan Daaboul, M.D.)]]
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 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 past medical history is also significant for tonic seizures. Today, her gait is wide-based and she has notable ataxia. She is severely mentally retarded, with a vocabulary of approximately 20 words. Despite these symptoms she has a pleasant demeanor and laughs often without humorous stimulus.]]
Answer A AnswerA::Deletion of a maternal-derived allele; methylation of a paternal-derived allele on chromosome 14
Answer A Explanation [[AnswerAExp::Angelman syndrome is caused by deletion of the maternal-derived allele and silencing of the paternal-derived allele on chromosome 15.]]
Answer B AnswerB::Deletion of paternal-derived allele; methylation of maternal-derived allele on chromosome 14
Answer B Explanation [[AnswerBExp::Angelman syndrome is caused by deletion of the maternal-derived allele and silencing of the paternal-derived allele on chromosome 15.]]
Answer C AnswerC::Deletion of maternal-derived allele; methylation of paternal-derived allele on chromosome 15
Answer C Explanation [[AnswerCExp::Angelman syndrome is caused by deletion of the maternal-derived allele and silencing of the paternal-derived allele on chromosome 15.]]
Answer D AnswerD::Deletion of paternal-derived allele; methylation of maternal-derived allele on chromosome 15
Answer D Explanation [[AnswerDExp::Angelman syndrome is caused by deletion of the maternal-derived allele and silencing of the paternal-derived allele on chromosome 15.]]
Answer E AnswerE::Methylation of two maternal-derived alleles on chromosome 15
Answer E Explanation [[AnswerEExp::Angelman syndrome is caused by deletion of the maternal-derived allele and silencing of the paternal-derived allele on chromosome 15.]]
Right Answer RightAnswer::C
Explanation [[Explanation::Angelman syndrome (AS), also known as the "happy puppet" syndrome, is a neurodevelopmental disorder characterized by severe intellectual and developmental disability, sleep disturbance, seizures, jerky movements (especially hand-flapping), frequent laughter or smiling, love of water, and usually a happy demeanor. Prominent facial features also include protruding jaw and tongue, deep set eyes, wide mouth, and flat occiput with microcephaly.

Angelman syndrome is most commonly caused by a deletions of in genes of maternal-derived alleles of chromosome 15. Other causes of AS include uniparental disomy for chromsome 15, imprinting (methylation) defect, and mutations within the gene that encode ubiquitin protein ligase (UBE3A).
Educational Objective: Angelman syndrome is caused by deletion of the normally imprinted maternal-derived allele on chromosome 15.
References: Clayton-Smith J, Laan L. Angelman syndrome: a review of the clinical and genetic aspects. J Med Genet. 2003;40:87-95.
First Aid 2104 page 85]]

Approved Approved::Yes
Keyword WBRKeyword::Angelman syndrome, WBRKeyword::Genetics, WBRKeyword::Imprinting, WBRKeyword::Epigenetics, WBRKeyword::Chromosome 15
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