A 21-year-old girl presents with primary amenorrhea. Examination shows an absent uterus, present breast development, and sparse pubic and axillary hair. What is the genetic etiology?

1. A

   A. MRKH

2. B

   B. Androgen insensitivity

3. C

   C. Turner's syndrome

4. D

   D. CAH

Appeared in: INI-CET EXAM -2026

Explanation

• The correct diagnosis is Androgen Insensitivity Syndrome (AIS), a 46,XY disorder of sex development.
• In AIS, the testes produce Anti-Müllerian Hormone, leading to the absence of the uterus and fallopian tubes.
• Testosterone produced by the testes is converted to estrogen, causing normal breast development (thelarche).
• The key diagnostic clue is sparse or absent pubic and axillary hair, which occurs because these tissues cannot respond to androgens due to defective receptors.

Why Other Options Were Wrong

• Option A: Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome presents with an absent uterus and normal breasts, but because these individuals are 46,XX with normal ovarian and adrenal function, they have a normal pattern of pubic and axillary hair.
• Option C: Turner's syndrome (45,X karyotype) is characterized by streak ovaries and estrogen deficiency. This results in an infantile (but present) uterus and a lack of spontaneous breast development.
• Option D: Congenital Adrenal Hyperplasia (CAH) in a 46,XX individual involves excess androgen production. This leads to a normal, present uterus and signs of virilization (like hirsutism), which is the opposite of the sparse hair seen in this patient.

Related Visual

Clinical Relevance

• Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Differential diagnosis of primary amenorrhea with Müllerian agenesis as background academic context rather than a clinical decision trigger.
• Nurses play a crucial role in providing sensitive psychosocial support to patients and families receiving a diagnosis of a disorder of sex development, as it has profound implications for identity, fertility, and sexual function.
• A key nursing intervention is patient education regarding the need for gonadectomy (removal of the testes) in individuals with AIS, typically after puberty, due to the increased risk of gonadal malignancy (gonadoblastoma).
• What if? If the patient had a normal uterus but no breast development, the differential diagnosis would shift towards conditions like hypothalamic amenorrhea or gonadal dysgenesis (e.g., Turner syndrome), and the initial workup would focus on FSH and LH levels.

How to Approach the Question

• First, analyze the core problem: primary amenorrhea in a 21-year-old.
• Next, evaluate the anatomical findings. The key finding is an absent uterus. This immediately narrows the differential to conditions like Müllerian agenesis (MRKH) or AIS.
• Then, assess the secondary sexual characteristics. The patient has present breast development (indicating estrogen effect) but sparse pubic/axillary hair (indicating lack of androgen effect).
• Synthesize the findings: The combination of an absent uterus, estrogen effects (breasts), and lack of androgen effects (hair) points directly to a 46,XY individual who is insensitive to androgens.
• Finally, compare this clinical picture to the options. Only Androgen Insensitivity Syndrome matches all the features. MRKH is ruled out by the sparse hair.

Concept Tested & Keywords

• Concept Tested: Differential diagnosis of primary amenorrhea with Müllerian agenesis.
• Stem keywords: primary amenorrhea, absent uterus, present breast development, sparse pubic and axillary hair
• Lead-in keywords: genetic etiology
• Clinical cues: The combination of an absent uterus with sparse pubic hair is a key indicator pointing away from MRKH and towards AIS.

Question ID

Qja7h8DmItvb81tebCXsDd

Copy ID

Reference Book

E6 Nelson Textbook of Pediatrics(2024) — Volume 2 p. 1156-1158

E6 Nelson Textbook of Pediatrics(2024) — Volume 1 p. 1222-1224