A patient presents with primary amenorrhea. On examination, she has normal breast and pubic hair development but no visible vagina. Which of the following is the most probable diagnosis?
**Core Concept**
The patient's presentation of primary amenorrhea with normal breast and pubic hair development suggests a specific issue with the development of the female reproductive system. This condition is often associated with abnormalities in the embryological development of the Müllerian ducts, which give rise to the female internal genitalia.
**Why the Correct Answer is Right**
The correct diagnosis is Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome, a congenital disorder characterized by the absence or underdevelopment of the vagina, cervix, and uterus. This condition occurs due to the failure of the Müllerian ducts to develop properly during embryogenesis. As a result, the patient has normal secondary sexual characteristics, including breast and pubic hair development, but lacks a visible vagina.
**Why Each Wrong Option is Incorrect**
**Option A:** Androgen Insensitivity Syndrome (AIS) typically presents with ambiguous genitalia, and the patient would have incomplete or absent pubic hair development due to the insensitivity to androgens.
**Option B:** Swyer syndrome is a condition characterized by a 46,XY karyotype, testes, and gonadal dysgenesis. Patients with Swyer syndrome typically have a more masculine phenotype and would not have normal breast and pubic hair development.
**Option C:** Congenital adrenal hyperplasia (CAH) can lead to virilization of female external genitalia, but the patient's presentation of normal breast and pubic hair development makes this diagnosis less likely.
**Clinical Pearl / High-Yield Fact**
It is essential to remember that primary amenorrhea can result from a variety of causes, including anatomical abnormalities, hormonal imbalances, and chromosomal disorders. A thorough physical examination and diagnostic workup are necessary to identify the underlying cause of primary amenorrhea.
**Correct Answer:** C.