WBR0390

Author	[[PageAuthor::Rim Halaby, M.D. [1]]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Genetics
Sub Category	SubCategory::Endocrine
Prompt	[[Prompt::A male patient presents to your office to inquire about a disease that is prevalent in his family. He is unsure what the disease is. Instead, he has a pedigree that he created that shows the list of affected and unaffected family members. The patient’s pedigree is shown below. What is the most likely disease in this patient’s family? File:X-linked dominant.png]]
Answer A	AnswerA::Leber’s hereditary optic neuropathy
Answer A Explanation	AnswerAExp::Leber’s hereditary optic neuropathy is a mitochondrial disease. All mitochondrial diseases are characterized by maternal transmission to all offspring.
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::A
Explanation	[[Explanation::The pedigree in the vignette shows an X-linked dominant pattern of inheritance. Daughters of affected fathers are also affected. Sons of affected mothers are also affected. Among the list of options, hypophosphatemic rickets, or vitamin D-resistant rickets, is the only option with X-linked dominant inheritance. It is characterized by increased phosphate wasting at the level of renal proximal tubule. Educational Objective: X-linked dominant inheritance pattern is characterized by transmission 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. Educational Objective: References: ]]
Approved	Approved::No
Keyword
Linked Question	Linked::
Order in Linked Questions	LinkedOrder::