A 17 year girl presented with absent thelarche and primary amenorrhea. On examination hypoplastic uterus was present. Investigation showed high FSH. Karyotype is XO. What is the probable diagnosis?
**Core Concept**
Turner syndrome is a chromosomal disorder characterized by the absence of one X chromosome, resulting in a 45,X karyotype. This condition is associated with various physical and reproductive abnormalities, including short stature, heart defects, and ovarian dysgenesis.
**Why the Correct Answer is Right**
The presence of high FSH levels in the context of a hypoplastic uterus and primary amenorrhea suggests ovarian failure. In Turner syndrome, the absence of one X chromosome leads to the degeneration of ovarian follicles, resulting in elevated FSH levels due to the loss of inhibitory feedback from estrogen. The karyotype of 45,X confirms the diagnosis of Turner syndrome.
**Why Each Wrong Option is Incorrect**
**Option A:** This is incorrect because Klinefelter syndrome is characterized by an extra X chromosome (47,XXY), which is not consistent with the karyotype of 45,X in this patient.
**Option B:** This is incorrect because androgen insensitivity syndrome is a condition where an individual with XY chromosomes is resistant to male hormones, resulting in a female phenotype. However, the karyotype of 45,X is not consistent with this diagnosis.
**Option C:** This is incorrect because premature ovarian failure can occur in various conditions, but the karyotype of 45,X and the presence of a hypoplastic uterus suggest a chromosomal cause, which is more consistent with Turner syndrome.
**Clinical Pearl / High-Yield Fact**
Turner syndrome is a classic example of a chromosomal disorder that affects ovarian development, leading to premature ovarian failure and infertility. It is essential to consider this diagnosis in patients with primary amenorrhea and a karyotype of 45,X.
**Correct Answer:** D. Turner syndrome.