WBR0114

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::Endocrine, SubCategory::Reproductive
Prompt	Prompt::A 15-year-old girl is evaluated for failure to experience menarche. The patient is 1.45 m (4’ 9”) tall, has a broad chest, low hairline and a webbed neck. Which of the following is most likely associated with this patient's condition?
Answer A	AnswerA::Increased LH, FSH, absence of functional SRY gene
Answer A Explanation	[[AnswerAExp::The SRY gene (also known as testis determining factor) is the gene on the Y chromosome that is responsible for the initiation of male sex in humans. Absence of functional SRY gene in an otherwise genetic male would cause Swyer syndrome. Swyer syndrome leads to phenotypic females with gonadal dysgenesis.]]
Answer B	AnswerB::Decreased LH, FSH, lack of Barr body
Answer B Explanation	[[AnswerBExp::While Turner syndrome is caused by the lack of a barr body, these patients typically have increased FSH and LH.]]
Answer C	AnswerC::Increased estrogen, preductal coarctation of the aorta
Answer C Explanation	AnswerCExp::While preductal coarction of the aorta is associated with Turner syndrome, the patients typically have decreased estrogen.
Answer D	AnswerD::Decreased estrogen, horsehoe kidney
Answer D Explanation	[[AnswerDExp::Turner syndrome is associated with horseshoe kidney and decreased estrogen due to gonadal dysgenesis.]]
Answer E	AnswerE::Decreased LH, FSH, infertile if untreated
Answer E Explanation	AnswerEExp::Turner syndrome patients have increased FSH and LH due to low levels of estrogen.
Right Answer	RightAnswer::D
Explanation	[[Explanation::The patient in this vignette is affected by Turner syndrome. Turner syndrome is caused by the lack of one copy of the X chromosome in females. Patients therefore have the genotype 45,XO. There are characteristic physical abnormalities, such as short stature, swelling, broad chest, low hairline, low-set ears, and webbed necks. Females with Turner syndrome typically experience gonadal dysfunction (non-working ovaries), which results in amenorrhea (absence of menstrual cycle) and sterility. Turner syndrome is also associated with cardiac abnormalities such as preductal coarctation of the aorta, and bicuspid aortic valve. Turner syndrome is associated with lymphatic dysfunction causing lymphedema of the hands and feet as well as cystic hygromas which result in the webbed neck phenotype. Patients can have renal abnormalities too, such as horseshoe kidney. A patient with Turner syndrome and webbed neck is pictured below. Educational Objective: Turner syndrome is associated with horshoe kidney and decreased estrogen due to gonadal dysgenesis. References: First Aid 2014 page 574 ; First Aid 2012 page 539 For a detailed discussion of Turner syndrome, see: Turner syndrome history and symptoms]]
Approved	Approved::Yes
Keyword	WBRKeyword::Reproductive, WBRKeyword::Chromosome, WBRKeyword::Karyotype, WBRKeyword::Turner syndrome, WBRKeyword::Ovulation, WBRKeyword::Genetics
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