FCPS part 1 Medicine solved mcqs with explanation Q19

Q19: A female with primary amenorrhea, webbed neck and a height of 141 cm. What would her karyotype show?

a) 45 XO

b) 45 XX

c) 46 XXY

d) 47 XYY

Correct Answer: a

Explanation:

Primary amenorrhea with a webbed neck and short stature( 141cm = 4’7”)is a classical presentation of Turner’s syndrome. The karyotype of Turner’s syndrome is 45 XO that is, one X chromosome is absent. Other features of Turner’s yndrome include streak ovaries (ovarian dysgenesis) and preductal coarctation of aorta. The patient is a female and has decreased estrogen and elevated FSH & LH levels.

It is the most common cause of primary amenorrhea.

Also in such patients there is no barr body. Since barr body is actually an inactivated X chromosome, and one X chromosome is only inactivated if one has two X chromosome. If there is already a single X chromosome, then it is not inactivated to form barr body. For this reason in Turner’s syndrome since there is only one X therefore there is no barr body.