Prenatal Diagnosis of 17-Hydroxylase/17,20-lyase Deficiency (17OHD) in a Case of 46,XY Sex Discordance and Low Maternal Serum Estriol

Background: A discrepancy between the fetal karyotype and the appearance of genitalia on ultrasound can be a diagnostic challenge. In these cases, it is difficult to shorten the extensive list of differential diagnoses without information on internal anatomy and endocrine profile. Case presentation: Here, we describe a diagnosis of 17-hydroxylase/17,20-lyase deficiency (17OHD), which was suspected based on low maternal serum estriol in the setting of 46,XY genitalia discordance. Through collaboration between maternal-fetal medicine and disorders of sex development (DSD) teams, the patient was counseled about the diagnosis and postnatal management plans were made. Conclusions: This case illustrates how prenatal diagnosis of this rare condition led to reduced parental stress and seamless transition to postnatal care.