A 15-year-old girl presents with primary amenorrhea. She has Tanner stage 5 breasts, Tanner stage 3 pubic hair, and a body mass index of 22 kg/m². There is no history of chronic illness or excessive exercise. Pelvic ultrasound shows a normal uterus and ovaries. What is the most likely cause of her primary amenorrhea?

• A Müllerian agenesis (Mayer-Rokitansky-Küster-Hauser syndrome)
• B Androgen insensitivity syndrome
• C Hypothalamic amenorrhea
• D Anatomic obstruction (e.g., transverse vaginal septum or imperforate hymen) ✓

Explanation

Primary amenorrhea with normal secondary sexual characteristics and a normal uterus on ultrasound points to an outflow tract obstruction. In Müllerian agenesis and androgen insensitivity, the uterus is absent on imaging, which rules out A and B. Hypothalamic amenorrhea typically presents with low BMI, excessive exercise, or stress, none of which are present here. An obstructed outflow tract (transverse vaginal septum or imperforate hymen) allows normal estrogen production and breast development but prevents menstrual shedding.

Reference: Nelson Textbook of Pediatrics, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.