SUN-170 Case of Complete Androgen Insensitivity Syndrome in a 7 Month Old Infant Presenting with Bilateral Inguinal Mass

Abstract Disclosure: R.H. Joaquin: None. K. Albano - Antiporda: None. J. Pipo - Deveza: None. Background: Androgen Insensitivity Syndrome (AIS) is a common cause of male disorders of sexual differentiation, affecting 1 in 20,000 genetic males. Its incidence in the Philippines remains unclear. AIS arises from insensitivity of the androgen receptor to androgen hormones due to a loss-of-function mutation in the androgen receptor (AR) gene on the X chromosome. Majority of patients with AIS present during puberty with primary amenorrhoea, but it can also be diagnosed early, with patients presenting with palpable gonads in the inguinal area or in the labia majora. Clinical Case: A 7-month-old infant with a female phenotype presented with bilateral inguinal masses noted during crying. Neonatal history included brief NICU admission for sepsis. Physical examination showed female external genitalia, prominent labia majora, underdeveloped labia minora, and two openings (urethra and vagina), with no hyperpigmentation or labial masses but bilateral inguinal masses. Imaging revealed bilateral testes and absent Müllerian structures (uterus and fallopian tubes). Karyotyping confirmed a 46 XY male karyotype. Disorder of sexual differentiation was considered, and hormone assays showed high AMH (>22.96 ng/mL; normal 0.53-7.78 ng/mL), high-normal Luteinizing hormone (6.8 mIU/mL; normal 0.02-7 mIU/mL), and elevated testosterone (2.62 ng/mL; normal 0.2-0.64 ng/mL). Genetic testing confirmed a pathogenic mutation in the AR gene, diagnosing the patient with Complete Androgen Insensitivity Syndrome (CAIS). Diagnosing CAIS requires clinical evaluation, biochemical testing, imaging, and genetic confirmation. Key findings include the absence of Müllerian structures on pelvic ultrasound, elevated AMH and testosterone levels, and a male karyotype. Genetic testing identifies AR gene mutations that cause androgen insensitivity. Management involves a multidisciplinary approach addressing medical, surgical, psychological, and reproductive aspects. Gonadectomy is typically delayed until adolescence due to the low malignancy risk in prepubertal individuals, allowing natural pubertal development. Hormone replacement therapy (HRT) is provided post-gonadectomy. Surgical options, such as vaginoplasty, may be considered based on patient preferences. Early genetic counseling is essential to support families in understanding CAIS and addressing its psychosocial impact. The patient is currently well, with normal growth and development but persistent bilateral inguinal masses. The family received genetic counseling for disease understanding and future childbearing considerations. Conclusion: CAIS is a rare disorder of sexual differentiation that may be misdiagnosed due to varied presentations. Early recognition and comprehensive diagnostic evaluation are crucial for timely and appropriate management. With proper care, individuals with CAIS can lead fulfilling lives. Presentation: Sunday, July 13, 2025