A 15-year-old female presents with primary amenorrhea, short stature (height below the 3rd percentile), a broad webbed neck, a low posterior hairline, and a wide carrying angle of the arms (cubitus valgus). Echocardiography reveals a bicuspid aortic valve and coarctation of the aorta. What is the karyotype in Turner syndrome?

Answer and explanation

Correct answer: D. 45,X

  1. Step 1: Synthesize clinical phenotype: Female with short stature, webbed neck, cubitus valgus, coarctation of the aorta, and primary ovarian dysgenesis (streak gonads).
  2. Step 2: Recognize genetic basis: Complete or partial monosomy of the X chromosome.
  3. Step 3: State standard karyotype: 45,X (found in approximately 50% of Turner syndrome cases, with the remainder exhibiting mosaicism or structural X anomalies).
Answer
45,X.
Why not the others: '47,XXY' is Klinefelter syndrome, presenting in tall males with gynecomastia and small testes; '47,XXX' is Triple X syndrome, often clinically normal; '46,XY with androgen insensitivity' produces a female phenotype with normal height and absent internal female reproductive organs.

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