View source for WBR0119

{{WBRQuestion
|QuestionAuthor=William J Gibson
|ExamType=USMLE Step 1
|MainCategory=Genetics
|SubCategory=Reproductive
|MainCategory=Genetics
|SubCategory=Reproductive
|MainCategory=Genetics
|SubCategory=Reproductive
|MainCategory=Genetics
|MainCategory=Genetics
|MainCategory=Genetics
|SubCategory=Reproductive
|MainCategory=Genetics
|SubCategory=Reproductive
|MainCategory=Genetics
|SubCategory=Reproductive
|MainCategory=Genetics
|SubCategory=Reproductive
|MainCategory=Genetics
|MainCategory=Genetics
|SubCategory=Reproductive
|Prompt=A 32 year old man is evaluated for infertility after 6 months of failed attempts at conception with his wife.  His wife has previously conceived and given birth to a healthy child in a separate relationship.  On physical exam, the patient has less muscle mass than most males, gynecomastia, and a lack of chest hair. Laboratory studies are significant for increased LH, increased FSH, low testosterone, low inhibin and high estrogen.  What is the most likely chromosomal status of this patient?
|Explanation=The patient in this vignette has Klinefelter’s syndrome.  Klinefelter’s syndrme is caused by the presence of two X chromosomes along with a single Y chromosome.  These individuals are phenotypically male but have hypogonadism.  Klinefelter’s syndrome is often diagnosed during workup for infertility.  The human genome has two copies of 22 autosomes (44 total) and two sex chromosomes, making 46 chromosomes total.  Klinefelter’s syndrome patients have one extra X.
|AnswerA=22, XO
|AnswerAExp=The human genome contains 2 copies of 22 autosomes (44 total) plus two sex chromosomes normally=46.
|AnswerB=23, XXY
|AnswerBExp=The human genome contains 2 copies of 22 autosomes (44 total) plus two sex chromosomes normally=46.
|AnswerC=45,XO
|AnswerCExp=45,XO is the karyotype seen in a [[Turner syndrome]] patient.
|AnswerD=46,XX/XY
|AnswerDExp=This karyotype refers to a rare mosaic chromosomal abnormality which causes some cells in the body to have XX chromosomes and some to have XY chromosomes.  This karyotype causes intersex conditions.
|AnswerE=47,XXY
|AnswerEExp=This karyotype is the karyotype of Klinefelters’ syndrome.
|EducationalObjectives=[[Klinefelter’s sydrome]] is caused by an extra X chromosome in an otherwise normal male.
|References=First Aid 2014 page 574
First Aid 2012 page 539
|RightAnswer=E
|WBRKeyword=Klinefelter syndrome, Sex, Chromosome, Genetics, Reproductive, Gender, Infertility
|Approved=Yes
}}