SAT-131 A Unique Case of Mullerian Agenesis Misdiagnosis

Abstract Disclosure: K.L. Yamamoto: None. Introduction: Mullerian agenesis occurs in roughly 1 in 4,500 to 5,000 females and typically presents as primary amenorrhea in female children. Its etiology is unclear, however patients with Mullerian agenesis are found to have hypoplasia or agenesis of structures derived from the Mullerian ducts, which include the upper vagina and the uterus. Other aspects of the female reproductive tract, such as the ovaries, are often structurally preserved and function normally leading to development of sexual secondary characteristics. Case: A 14 year old female presented to her pediatrician with complaints of amenorrhea and delayed development, with her exam notable for scant pubic hair but otherwise no development of secondary sexual characteristics including breast growth. Her initial labs denoted a hypergonadotropic hypogonad state, with an undetectable serum estradiol level and serum FSH and LH levels of 143.2 mIU/L and 62 mIU/mL respectively. Her other workup included a 46,XX karyotype, normal prolactin level of 16.1 ng/mL, TSH level of 2.09 mIU/L, total testosterone level of 29 ng/dL, a negative 21-hydroxylase antibody, a normal 17-hydroxyprogesterone level, and an anti-mullerian hormone level of less than 0.003 ng/mL. A pelvic ultrasound showed unusually small ovaries without any evidence of a cervix or uterus, with subsequent abdominal MRI showing no distinct follicle containing ovaries and the absence of a uterus and cervix. She was then referred to pediatric endocrinology, where she was given a diagnosis of Mullerian agenesis and started on escalating estradiol patch doses for puberty induction. She was counseled that fertility would be limited to in vitro fertilization with surrogacy. Roughly one year after initiation of estradiol, she began to note not only development of secondary sexual characteristics, but also monthly cyclical vaginal bleeding. A pelvic exam was performed where she was found to have a visible cervix and palpable uterus with follow-up ultrasound showing a uterus measuring 6.4 x 2.0 x 2.9 cm and a right ovary measuring 2.0 x 1.2 cm; her left ovary was not visualized. At this point, she was given a new diagnosis of 46,XX gonadal dysgenesis and started on monthly medroxyprogesterone acetate for endometrial protection.Conclusion: In a female patient with gonadal dysgenesis and resultant estrogen deficiency, initially compromised uterine growth can result in a uterus too small to see on imaging and a misdiagnosis of Mullerian agenesis until estradiol therapy is started, after which uterine growth can occur and subsequently be visualized. Presentation: Saturday, July 12, 2025