A 19-year old patient complains of primary amenorrhea. She had well developed breast and public hair but on examination there was absence of uterus and vagina. Likely diagnosis is:
**Core Concept**
The patient's presentation of primary amenorrhea with well-developed breast and pubic hair but absence of uterus and vagina suggests a disorder of sex development (DSD). This condition involves atypical development of the gonads, sex chromosomes, or external genitalia.
**Why the Correct Answer is Right**
The likely diagnosis in this case is Androgen Insensitivity Syndrome (AIS), a form of complete androgen insensitivity. This occurs when a genetically male individual (46,XY) has a mutation in the androgen receptor gene, rendering them unresponsive to androgens. As a result, the Wolffian ducts (which develop into the epididymis, vas deferens, and seminal vesicles in males) regress, and the Müllerian ducts (which develop into the uterus, fallopian tubes, and upper part of the vagina in females) fail to develop. The individual develops female external genitalia despite having testes and a 46,XY karyotype.
**Why Each Wrong Option is Incorrect**
**Option A:** Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome is a condition characterized by congenital absence of the uterus and upper vagina in individuals with a normal 46,XX karyotype. However, it is not associated with the absence of pubic hair and breast development.
**Option B:** Congenital adrenal hyperplasia (CAH) is a group of genetic disorders that affect the adrenal glands. While CAH can lead to virilization of a genetically female individual, it would not explain the absence of a uterus and vagina.
**Option C:** Swyer syndrome is a form of sex reversal where a genetically male individual (46,XY) develops as a phenotypic female due to a mutation in the SRY gene. However, it is not typically associated with the absence of pubic hair and breast development.
**Clinical Pearl / High-Yield Fact**
A key clinical feature of Androgen Insensitivity Syndrome is the presence of testes in a phenotypic female, which can increase the risk of testicular cancer.
**Correct Answer:** C.