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{{WBRQuestion
{{WBRQuestion
|QuestionAuthor={{Rim}}, {{AJL}} {{Alison}}
|QuestionAuthor= {{YD}} (Reviewed by  {{YD}} and  {{AJL}})
|ExamType=USMLE Step 1
|ExamType=USMLE Step 1
|MainCategory=Genetics
|MainCategory=Genetics
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|MainCategory=Genetics
|MainCategory=Genetics
|SubCategory=Endocrine
|SubCategory=Endocrine
|MainCategory=Genetics
|MainCategory=Genetics
|MainCategory=Genetics
|MainCategory=Genetics
|MainCategory=Genetics
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|MainCategory=Genetics
|MainCategory=Genetics
|SubCategory=Endocrine
|SubCategory=Endocrine
|Prompt=A 32-year-old male patient presents to your office to inquire about a disease, which is prevalent in his family. He does not recall the name of the disease. Instead, he provides you with a pedigree, which an old physician created, illustrating a the affected and unaffected family members. The patient’s pedigree is displayed below. Which of the following diseases most likely prevails in this patient’s family?
|Prompt=A 32-year-old man presents to the physician's office to inquire about a disease that is prevalent in his family. He is unsure what the disease is. Instead, he creates a family tree that demonstrates all the affected and unaffected family members. The patient’s family tree is shown below. What is the most likely disease in this patient’s family?
 
[[Image:X-linked-dominant.gif|700px]]
|Explanation=The pedigree in this scenario demonstrates an X-linked dominant pattern of inheritance.  In almost every scenario, daughters of affected fathers acquire the disease and sons of affected mothers are aquire the disease.  Among the list of options, [[hypophosphatemic rickets]], or vitamin D-resistant rickets, is the only disease with X-linked dominant inheritance.  [[Hypophosphatemic rickets]] are characterized by the increased waste of phosphate at the renal proximal tubule level.
 
EducationalObjectives= An X-linked dominant inheritance pattern is characterized by transmission from affected fathers to daughters and affected mothers to sons. [[Hypophosphatemic rickets]] are an example of an X-linked dominant inheritance pattern, which causes phosphate wasting at the level of renal proximal tubules.
|References= First Aid 2014 page 86
 


[[Image:WBR0390.gif|700px]]
|Explanation=The pedigree demonstrates an X-linked dominant pattern of inheritance. X-linked dominant inheritance pattern is characterized by inheritance of disease from affected fathers to daughters and affected mothers to sons. Among the list of options, [[hypophosphatemic rickets]] (vitamin D-resistant rickets) is the only disease with X-linked dominant pattern of inheritance. [[Hypophosphatemic rickets]] is caused by a mutation in the ''PHEX'' gene and is characterized by increased phosphate wasting at the level of the renal proximal convoluted tubule. It is the most common cause of familial hypophosphatemia. The onset of manifestations is usually during childhood with a wide range of clinical features. Severe forms are associated with bone deformities (e.g. osteomalacia, knock knees, and bowed legs), abnormal growth, and dental abnormalities.
|AnswerA=Leber’s hereditary optic neuropathy
|AnswerA=Leber’s hereditary optic neuropathy
|AnswerAExp=[[Leber’s hereditary optic neuropathy]] is a mitochondrial disease.  All mitochondrial diseases are characterized by maternal transmission to offspring.
|AnswerAExp=[[Leber’s hereditary optic neuropathy]] is a mitochondrial disease, which is maternally inherited.
|AnswerB=Albinism
|AnswerB=Albinism
|AnswerBExp=[[Albinism]] has an autosomal recessive mode of inheritance.
|AnswerBExp=[[Albinism]] has an autosomal recessive mode of inheritance.
|AnswerC=Hypophosphatemic rickets
|AnswerC=Hypophosphatemic rickets
|AnswerCExp=[[Hypophosphatemic rickets]] have an X-linked dominant mode of inheritance.
|AnswerCExp=[[Hypophosphatemic rickets]] has an X-linked dominant mode of inheritance.
|AnswerD=Ocular albinism
|AnswerD=Ocular albinism
|AnswerDExp=Ocular albinism has an X-linked recessive mode of inheritance.
|AnswerDExp=Ocular albinism has an X-linked recessive mode of inheritance.
|AnswerE=Schizophrenia
|AnswerE=Schizophrenia
|AnswerEExp=Schizophrenia has a polygenic mode of inheritance.
|AnswerEExp=Schizophrenia has a polygenic mode of inheritance.
|EducationalObjectives=X-linked dominant inheritance pattern is characterized by inheritance of disease from affected fathers to daughters and affected mothers to sons. Hypophosphatemic rickets is an example of X-linked dominant inheritance pattern that causes phosphate wasting at the level of renal proximal tubule.
|References=Carpenter TO, Imel EA, Holm IA, et al. A clinician's guide to X-linked hypophosphatemia. J Bone Mineral Res. 2011;26(7):1381-8.<br>
First Aid 2014 page 86
|RightAnswer=C
|RightAnswer=C
|AnswerEExp= X-linked, X-linked dominant, pedigree, genetics, inheritance, Hypophosphatemic rickets, transmission, inheritance pattern
|WBRKeyword=X-linked, X-linked dominant, Pedigree, Inheritance, Hypophosphatemic rickets, Inheritance pattern
|Approved=Yes
|Approved=Yes
}}
}}

Latest revision as of 00:25, 28 October 2020
Author [[PageAuthor::Yazan Daaboul, M.D. (Reviewed by Yazan Daaboul, M.D. and Alison Leibowitz [1])]]
Exam Type ExamType::USMLE Step 1
Main Category MainCategory::Genetics
Sub Category SubCategory::Endocrine
Prompt [[Prompt::A 32-year-old man presents to the physician's office to inquire about a disease that is prevalent in his family. He is unsure what the disease is. Instead, he creates a family tree that demonstrates all the affected and unaffected family members. The patient’s family tree is shown below. What is the most likely disease in this patient’s family?

]]

Answer A AnswerA::Leber’s hereditary optic neuropathy
Answer A Explanation [[AnswerAExp::Leber’s hereditary optic neuropathy is a mitochondrial disease, which is maternally inherited.]]
Answer B AnswerB::Albinism
Answer B Explanation [[AnswerBExp::Albinism has an autosomal recessive mode of inheritance.]]
Answer C AnswerC::Hypophosphatemic rickets
Answer C Explanation [[AnswerCExp::Hypophosphatemic rickets has an X-linked dominant mode of inheritance.]]
Answer D AnswerD::Ocular albinism
Answer D Explanation AnswerDExp::Ocular albinism has an X-linked recessive mode of inheritance.
Answer E AnswerE::Schizophrenia
Answer E Explanation AnswerEExp::Schizophrenia has a polygenic mode of inheritance.
Right Answer RightAnswer::C
Explanation [[Explanation::The pedigree demonstrates an X-linked dominant pattern of inheritance. X-linked dominant inheritance pattern is characterized by inheritance of disease from affected fathers to daughters and affected mothers to sons. Among the list of options, hypophosphatemic rickets (vitamin D-resistant rickets) is the only disease with X-linked dominant pattern of inheritance. Hypophosphatemic rickets is caused by a mutation in the PHEX gene and is characterized by increased phosphate wasting at the level of the renal proximal convoluted tubule. It is the most common cause of familial hypophosphatemia. The onset of manifestations is usually during childhood with a wide range of clinical features. Severe forms are associated with bone deformities (e.g. osteomalacia, knock knees, and bowed legs), abnormal growth, and dental abnormalities.

Educational Objective: X-linked dominant inheritance pattern is characterized by inheritance of disease from affected fathers to daughters and affected mothers to sons. Hypophosphatemic rickets is an example of X-linked dominant inheritance pattern that causes phosphate wasting at the level of renal proximal tubule.
References: Carpenter TO, Imel EA, Holm IA, et al. A clinician's guide to X-linked hypophosphatemia. J Bone Mineral Res. 2011;26(7):1381-8.
First Aid 2014 page 86]]

Approved Approved::Yes
Keyword WBRKeyword::X-linked, WBRKeyword::X-linked dominant, WBRKeyword::Pedigree, WBRKeyword::Inheritance, WBRKeyword::Hypophosphatemic rickets, WBRKeyword::Inheritance pattern
Linked Question Linked::
Order in Linked Questions LinkedOrder::
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