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?]]
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::