MRI Evaluation of a 46, XX Disorder of Sex Development Due to Classical 21-Hydroxylase Deficiency Congenital Adrenal Hyperplasia in a 6-Month-Old Infant: A Case Report

Background: Classical congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency is the most common cause of 46,XX disorders of sex development (DSD), resulting in androgenic virilization of the female external genitalia. Magnetic resonance imaging (MRI) plays a central and increasingly indispensable role in the non-invasive characterization of internal genitourinary anatomy and in guiding multidisciplinary management.
Case Presentation: We report a 6-month-old infant registered as male at birth, followed for classical CAH due to 21-hydroxylase deficiency with bilateral adrenal hyperplasia on imaging, subsequently found to have a 46,XX karyotype on genetic testing. Clinical examination revealed pseudo-masculine external genitalia with Prader stage IV–V virilization and bilaterally non-palpable gonads. Biochemical workup confirmed markedly elevated 17-hydroxyprogesterone (17-OHP) and adrenal androgens. Pelvic MRI demonstrated probable clitoromegaly, an identifiable urogenital sinus with a vaginal component, a small median uterus with visible endometrium, bilateral hypoplastic ovarian structures, absence of any male gonadal structure, and left adrenal gland enlargement — consistent with 46,XX DSD with advanced virilization.
Conclusion: MRI is a valuable, non-irradiating modality for the comprehensive evaluation of internal genitourinary anatomy in 46,XX DSD secondary to CAH, providing essential information for sex assignment, surgical planning, and multidisciplinary management decisions.