USMLE Step 1

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Biochemistry

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Chromosomal Abnormalities

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Turner Syndrome

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Turner Syndrome, also known as 45,X or 45,XO, is a chromosomal defect affecting females that results from the loss or partial loss of a X-chromosome.

The lack of an second X chromosome results in defective ovarian development. This may present in adolescent females as amenorrhea (lack of menses), with a lack of secondary sex characteristics. Ultrasound imaging reveals streak ovaries. Defective ovaries result in reduced estrogen levels, with compensatory elevation in LH and FSH.

Other physical findings include a short statue, webbed neck, cystic hygroma, and lymphedema. Cardiovascular complications include coarctation of the aorta, and a bicuspid aortic valve (increased risk for aortic stenosis).

Find Turner Syndrome and more Chromosomal Abnormalities among Pixorize's visual mnemonics for the USMLE Step 1 and NBME Shelf Exams.