Question

Primary amenorrhea with absent uterus, normal breasts and scant pubic hair is seen in:

• A. Mayer Rokitansky Kuster Hauser syndrome
• B. Turner's syndrome
• C. Androgen insensitivity syndrome
• D. Noonan syndrome

Hint:

Normal breasts but scant pubic hair is the androgen insensitivity giveaway.

Answer 1

The Correct Option is C

Step 1: Break the stem into three findings: absent uterus, normal breasts, and scant or absent pubic hair. Each finding narrows the diagnosis.
Step 2: Absent uterus means the Mullerian structures regressed, which happens when AMH is present, that is, when testes exist (46,XY) or when Mullerian agenesis occurs.
Step 3: Normal breasts mean estrogen is active. In androgen insensitivity syndrome (AIS), the testosterone made by the testes is converted to estrogen and, because androgen action is blocked, this estrogen drives normal female breast development.
Step 4: Scant pubic hair is the key separator. Pubic and axillary hair depend on androgens. In AIS the androgen receptor is defective, so sexual hair is sparse or absent. This is the hallmark that points to AIS over Mullerian agenesis.
Step 5: Compare the distractors.
MRKH (option A): also has absent uterus and normal breasts, but pubic hair is NORMAL because the ovaries and androgen response are intact. So scant hair excludes MRKH.
Turner syndrome (option B): has a uterus present, streak ovaries, poor breast development and short stature; does not fit.
Noonan syndrome (option D): not a cause of this picture.
The combination of absent uterus, normal breasts and scant pubic hair is classic for AIS. The answer is option C.