A 25-year-old woman with amenorrhea has never had menarche. On physical examination, she is 145 cm (4 ft 9 in) tall. She has a webbed neck, a broad chest, and widely spaced nipples. Strong pulses are palpable in the upper extremities, but there are only weak pulses in the lower extremities. On abdominal MR imaging, her ovaries are small, elongated, and tubular. Which of the following karyotypes is she most likely to have?

**Core Concept**
Turner syndrome is a genetic disorder characterized by the complete or partial absence of one X chromosome, leading to gonadal dysgenesis and various physical abnormalities. The condition is often associated with short stature, cardiac anomalies, and infertility.

**Why the Correct Answer is Right**
The patient's clinical presentation, including short stature, webbed neck, broad chest, widely spaced nipples, and weak lower limb pulses, is suggestive of Turner syndrome. The presence of small, elongated, and tubular ovaries on abdominal MR imaging further supports this diagnosis. The most common karyotype associated with Turner syndrome is 45,X, which is a result of monosomy X. However, mosaicism, where both 45,X and 46,XX cells are present, is also possible. The patient's karyotype of 45,X/46,XX reflects this mosaicism, where some cells have lost one X chromosome, while others have the typical 46,XX karyotype.

**Why Each Wrong Option is Incorrect**
**Option B:** 46, X, X (fra) is a karyotype associated with X-linked ichthyosis, a condition characterized by dry, scaly skin and impaired testosterone production. This karyotype is not associated with Turner syndrome.
**Option C:** 47, XXY is the karyotype associated with Klinefelter syndrome, a genetic disorder affecting males, characterized by tall stature, infertility, and developmental delays.
**Option D:** 47, XXX is a karyotype associated with trisomy X, also known as triple X syndrome, a condition affecting females, characterized by tall stature, delayed speech, and learning difficulties.

**Clinical Pearl / High-Yield Fact**
Turner syndrome is often associated with cardiac anomalies, particularly bicuspid aortic valve and coarctation of the aorta. Patients with Turner syndrome require regular cardiac evaluation to prevent complications.

**✓ Correct Answer: A. 45, X/46, XX**

✓ Correct Answer: A. 45, X/46, XX