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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
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|MainCategory=Genetics
|MainCategory=Genetics
|SubCategory=Endocrine, Reproductive
|SubCategory=Endocrine, Reproductive
|MainCategory=Genetics
|MainCategory=Genetics
|MainCategory=Genetics
|MainCategory=Genetics
|MainCategory=Genetics
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|MainCategory=Genetics
|MainCategory=Genetics
|SubCategory=Endocrine, Reproductive
|SubCategory=Endocrine, Reproductive
|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?
|Prompt=A 14-year-old girl is evaluated for failure to experience menarche. The patient is 1.45 m (4’ 9”) tall, has downward slanting of the eyes, low hairline, and a webbed neck. Further inspection reveals a broad chest and increased carrying angle of the elbow. Which of the following findings are most likely associated with this patient's condition?
|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 neck]]s.  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 hygroma]]s which result in the webbed neck phenotype. Patients can have renal abnormalities too, such as [[horseshoe kidney]].
|Explanation=Turner syndrome is caused by the a complete or partial loss of one copy of the X chromosome, an abnormal structure of the X chromosome, or mosaicim of a 45,XO cell line with another cell line. The karyotype of patients with Turner syndrome is 45,XO. Turner syndrome affects 1/2000 to 1/3000 live-born girls. It has a variable phenotypic expression, but some features are common.
 
A patient with Turner syndrome and webbed neck is pictured below.


[[File:Neck Turner.JPG]]
Facial characteristics include abnormalities caused by lymphatic obstruction, such redundant neck folds, low posterior hairlines, and neck webbing (pterygium colli). Other signs of obstructive lymphedema include cystic hygroma, acral congenital lymphedema, and interstitial congestion. Also, patients have posteriorly rotated ears, downward slanting of the eyes, and epicanthal folds. Skeletal features include short stature, congenital hip dislocation, scoliosis, broad shield-shaped chest with a square torso and widely spaced nipples, and cubitus valgus (increased carrying angle of the elbow). Patients often also have dental crowding, micrognathia or prognathia, and a posterior rotation of the mandible.
|AnswerA=Increased LH, FSH, absence of functional SRY gene
|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.
|AnswerB=Decreased LH, FSH, lack of Barr body
|AnswerBExp=While Turner syndrome is caused by the lack of a [[Barr body]], these patients typically have increased [[FSH]] and [[LH]].
|AnswerC=Increased estrogen, preductal coarctation of the aorta
|AnswerCExp=While preductal coarction of the aorta is associated with Turner syndrome, the patients typically have decreased estrogen.
|AnswerD=Decreased estrogen, horsehoe kidney
|AnswerDExp=Turner syndrome is associated with [[horseshoe kidney]] and decreased estrogen due to gonadal dysgenesis.
|AnswerE=Decreased LH, FSH, infertile if untreated
|AnswerEExp=Turner syndrome patients have increased FSH and LH due to low levels of estrogen.
|EducationalObjectives=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]]
Females with Turner syndrome typically experience gonadal dysgenesis (or less commonly agenesis), which results in amenorrhea, infertility, and the presence of a hypoplastic uterus due to low estrogen levels. Consequently, the loss of negative feedback inhibition results in elevated FSH and LH levels. Turner syndrome is also associated with cardiac abnormalities such as pre-ductal coarctation of the aorta (delayed femoral pulses), and bicuspid aortic valve. Turner syndrome is also associated with the presence of a horseshoe kidney, a renal fusion anomaly that leads to trapping of the fused kidney low in the abdomen under the inferior mesenteric artery.
|AnswerA=Elevated LH and FSH levels with absence of functional ''SRY'' gene
|AnswerAExp=The ''[[SRY]]'' gene encodes the SRY protein, which is also known as  testis determining factor (TDF). It is located on the Y chromosome and is responsible for the initiation of male sex determination. Absence of functional ''SRY'' gene in an otherwise genetic male would cause [[Swyer syndrome]], which is characterized by presence of phenotypic females with gonadal dysgenesis.
|AnswerB=Decreased LH and FSH levels with absence of Barr body
|AnswerBExp=While Turner syndrome is caused by the absence of a [[Barr body]] in somatic cells of females, these patients typically have increased [[FSH]] and [[LH]] due to loss of feedback inhibition by gonadal hormones.
|AnswerC=Elevated estrogen levels with preductal coarctation of the aorta
|AnswerCExp=While preductal coarction of the aorta is associated with Turner syndrome, patients typically have decreased levels of estrogen due to ovarian dysgenesis.
|AnswerD=Decreased estrogen levels with a renal fusion anomaly
|AnswerDExp=Turner syndrome is associated with presence of a [[horseshoe kidney]] and decreased estrogen due to gonadal dysgenesis.
|AnswerE=Elevated LH and FSH levels with ovarian dysgenesis and a normal uterus
|AnswerEExp=Patients with Turner syndrome have elevated FSH and LH due to loss of feedback inhibition caused by abnormally low estrogen levels. The majority of patients have a form of ovarian dysgenesis (or less commonly agenesis). Ovaries eventually become fibrotic, resulting in "streak ovaries". Although present, the uterus of patients with Turner syndrome is typically hypoplastic due to persistently low levels of estrogen during childhood.
|EducationalObjectives=Turner syndrome is associated with [[horseshoe kidney]], a renal fusion anomaly, and ovarian dysgenesis, which leads to low estrogen levels, elevated FSH and LH, and a hypoplastic uterus.
|References=Doswell BH, Visootsak J, Brady AN, Graham JM. Turner syndrome: an update and review for the primary pediatrician. Clin Pediatr. 2006;45:301-13.<br>
First Aid 2014 page 574
|RightAnswer=D
|RightAnswer=D
|WBRKeyword=Reproductive, Chromosome, Karyotype, Turner syndrome, Ovulation, Genetics,
|WBRKeyword=Reproductive, Chromosome, Karyotype, Turner syndrome, Ovulation, Genetics, Turner's syndrome, Horseshoe kidney, Lymphedema, Webbed neck, Short stature
|Approved=Yes
|Approved=Yes
}}
}}

Latest revision as of 23:23, 27 October 2020

 
Author [[PageAuthor::William J Gibson (Reviewed by Yazan Daaboul, M.D.)]]
Exam Type ExamType::USMLE Step 1
Main Category MainCategory::Genetics
Sub Category SubCategory::Endocrine, SubCategory::Reproductive
Prompt [[Prompt::A 14-year-old girl is evaluated for failure to experience menarche. The patient is 1.45 m (4’ 9”) tall, has downward slanting of the eyes, low hairline, and a webbed neck. Further inspection reveals a broad chest and increased carrying angle of the elbow. Which of the following findings are most likely associated with this patient's condition?]]
Answer A AnswerA::Elevated LH and FSH levels with absence of functional ''SRY'' gene
Answer A Explanation [[AnswerAExp::The SRY gene encodes the SRY protein, which is also known as testis determining factor (TDF). It is located on the Y chromosome and is responsible for the initiation of male sex determination. Absence of functional SRY gene in an otherwise genetic male would cause Swyer syndrome, which is characterized by presence of phenotypic females with gonadal dysgenesis.]]
Answer B AnswerB::Decreased LH and FSH levels with absence of Barr body
Answer B Explanation [[AnswerBExp::While Turner syndrome is caused by the absence of a Barr body in somatic cells of females, these patients typically have increased FSH and LH due to loss of feedback inhibition by gonadal hormones.]]
Answer C AnswerC::Elevated estrogen levels with preductal coarctation of the aorta
Answer C Explanation AnswerCExp::While preductal coarction of the aorta is associated with Turner syndrome, patients typically have decreased levels of estrogen due to ovarian dysgenesis.
Answer D AnswerD::Decreased estrogen levels with a renal fusion anomaly
Answer D Explanation [[AnswerDExp::Turner syndrome is associated with presence of a horseshoe kidney and decreased estrogen due to gonadal dysgenesis.]]
Answer E AnswerE::Elevated LH and FSH levels with ovarian dysgenesis and a normal uterus
Answer E Explanation [[AnswerEExp::Patients with Turner syndrome have elevated FSH and LH due to loss of feedback inhibition caused by abnormally low estrogen levels. The majority of patients have a form of ovarian dysgenesis (or less commonly agenesis). Ovaries eventually become fibrotic, resulting in "streak ovaries". Although present, the uterus of patients with Turner syndrome is typically hypoplastic due to persistently low levels of estrogen during childhood.]]
Right Answer RightAnswer::D
Explanation [[Explanation::Turner syndrome is caused by the a complete or partial loss of one copy of the X chromosome, an abnormal structure of the X chromosome, or mosaicim of a 45,XO cell line with another cell line. The karyotype of patients with Turner syndrome is 45,XO. Turner syndrome affects 1/2000 to 1/3000 live-born girls. It has a variable phenotypic expression, but some features are common.

Facial characteristics include abnormalities caused by lymphatic obstruction, such redundant neck folds, low posterior hairlines, and neck webbing (pterygium colli). Other signs of obstructive lymphedema include cystic hygroma, acral congenital lymphedema, and interstitial congestion. Also, patients have posteriorly rotated ears, downward slanting of the eyes, and epicanthal folds. Skeletal features include short stature, congenital hip dislocation, scoliosis, broad shield-shaped chest with a square torso and widely spaced nipples, and cubitus valgus (increased carrying angle of the elbow). Patients often also have dental crowding, micrognathia or prognathia, and a posterior rotation of the mandible.

Females with Turner syndrome typically experience gonadal dysgenesis (or less commonly agenesis), which results in amenorrhea, infertility, and the presence of a hypoplastic uterus due to low estrogen levels. Consequently, the loss of negative feedback inhibition results in elevated FSH and LH levels. Turner syndrome is also associated with cardiac abnormalities such as pre-ductal coarctation of the aorta (delayed femoral pulses), and bicuspid aortic valve. Turner syndrome is also associated with the presence of a horseshoe kidney, a renal fusion anomaly that leads to trapping of the fused kidney low in the abdomen under the inferior mesenteric artery.
Educational Objective: Turner syndrome is associated with horseshoe kidney, a renal fusion anomaly, and ovarian dysgenesis, which leads to low estrogen levels, elevated FSH and LH, and a hypoplastic uterus.
References: Doswell BH, Visootsak J, Brady AN, Graham JM. Turner syndrome: an update and review for the primary pediatrician. Clin Pediatr. 2006;45:301-13.
First Aid 2014 page 574]]

Approved Approved::Yes
Keyword WBRKeyword::Reproductive, WBRKeyword::Chromosome, WBRKeyword::Karyotype, WBRKeyword::Turner syndrome, WBRKeyword::Ovulation, WBRKeyword::Genetics, WBRKeyword::Turner's syndrome, WBRKeyword::Horseshoe kidney, WBRKeyword::Lymphedema, WBRKeyword::Webbed neck, WBRKeyword::Short stature
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