Question:easy
A female presents with an XO genotype and primary amenorrhoea. What is the most likely diagnosis?
A female presents with an XO genotype and primary amenorrhoea. What is the most likely diagnosis?
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XO equals Turner syndrome; the ovaries become non-functional streak gonads.
Updated On: Jun 24, 2026
- Gonadal dysgenesis
- Androgen insensitivity syndrome
- Mayer-Rokitansky-Kuster-Hauser (MRKH) syndrome
- Congenital adrenal hyperplasia (CAH)
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The Correct Option is A
Solution and Explanation
Begin with the chromosome count. The notation XO means there are 45 chromosomes with only one sex chromosome, the hallmark of Turner syndrome. A patient who lacks the second X cannot keep her ovaries functioning, so during fetal life the germ cells are lost and the gonads degenerate into thin fibrous bands called streak gonads. This failure of the gonad to form properly is exactly what the term gonadal dysgenesis describes. Because the streak gonads make almost no oestrogen, the uterus stays small, breasts do not develop, and a period never arrives, which is reported as primary amenorrhoea; the pituitary responds to the low oestrogen by driving FSH and LH very high. Compare this with the distractors: androgen insensitivity carries a male XY pattern with hidden testes, MRKH keeps a normal female XX pattern and working ovaries but is missing the uterus and upper vagina, and congenital adrenal hyperplasia goes with XX plus virilisation from excess adrenal androgens. None of these matches an XO result, so the single answer that fits the XO patient with no menstruation is gonadal dysgenesis. $XO \rightarrow$ Turner syndrome $\rightarrow$ streak gonads.\[\boxed{\text{Gonadal dysgenesis}}\]
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