Differential Diagnosis for Primary Amenorrhea
The patient presents with primary amenorrhea, defined as the absence of menstruation by the age of 16 in the presence of normal secondary sexual characteristics, or within 4 years after breast development begins. Given the clinical findings, the following differential diagnoses are considered:
Single Most Likely Diagnosis
- Mayer-Rokitansky-Küster-Hauser (MRKH) Syndrome: This condition is characterized by the congenital absence of the uterus and vagina, which aligns with the patient's pelvic examination findings (absence of the cervix and a well-rugated vagina) and pelvic ultrasonography results (absence of the uterus). The presence of normal ovarian function (indicated by normal FSH levels and Tanner stage 4 breast development) and a 46,XX karyotype further supports this diagnosis.
Other Likely Diagnoses
- Androgen Insensitivity Syndrome (AIS): Although less likely given the normal FSH level and the absence of the uterus, AIS could be considered if there were any signs of androgen resistance. However, the patient's presentation does not strongly suggest AIS, especially with the presence of pubic hair (Tanner stage 4), which is often absent or sparse in individuals with complete AIS.
- Gonadal Dysgenesis: This condition involves abnormal development of the gonads and could lead to primary amenorrhea. However, the patient's normal FSH level and 46,XX karyotype make this less likely.
Do Not Miss Diagnoses
- Obstructed Uterovaginal Anomalies: Conditions such as imperforate hymen or transverse vaginal septum could cause primary amenorrhea due to obstruction of menstrual flow. Although the speculum examination did not reveal a cervix, an obstructed uterovaginal anomaly could still be present and would require further imaging or surgical evaluation to diagnose.
- Pituitary or Hypothalamic Lesions: Although the patient's FSH level is within the normal range, central causes of amenorrhea (e.g., pituitary tumors, hypothalamic amenorrhea) should be considered, especially if there are other symptoms such as headaches or visual disturbances.
Rare Diagnoses
- Congenital Adrenal Hyperplasia (CAH): This is a group of inherited disorders that affect the adrenal glands, leading to hormone imbalances. While CAH can cause amenorrhea, it typically presents with other symptoms such as virilization or Cushingoid features, which are not mentioned in the patient's presentation.
- Turner Syndrome: Characterized by a 45,X karyotype, Turner syndrome often presents with short stature and gonadal dysgenesis. The patient's normal height and 46,XX karyotype make this diagnosis unlikely.
- Swyer Syndrome: This rare condition involves a 46,XY karyotype with streak gonads and typically presents with primary amenorrhea. However, the patient's 46,XX karyotype and presence of normal secondary sexual characteristics make this diagnosis unlikely.