P395: Chromosomal rearrangements resulting in Beckwith-Wiedemann syndrome and beyond

to the uncertainty of sexual development in these rare cases, close surveillance is recommended to monitor for appropriate development.Due to the paucity of literature of these cases, unanswered questions related to long-term ovarian function, reproduction, and long-term risk for gonadoblastomas and germ cell tumors remain.Conclusion: This raises additional inquiries about the developmental timing and gene dosage context of genes involved in sexual development.Introduction: Patients with a 47, XXY karyotype, Klinefelter syndrome, typically present clinically as non-ambiguous males due to the presence of SRY in the Y Chromosome.The SRY gene (sex-determining region Y) provides instructions for early gonadal determination.Individuals with this karyotype are almost exclusively phenotypically male with development of testicular failure during the second decade of life.There have been 16 cases reported of females with 47, XXY karyotypes.Most of these cases were diagnosed with androgen insensitivity syndrome.However, there have been a handful of cases of 47, XXY phenotypic females with normal internal and external female genitalia.Case Presentation: We present a case of a 2-year-old patient that is phenotypically female with normal female external and internal genitalia in the absence of sexual development ambiguity.This patient first presented to medical genetics prenatally with an abnormal prenatal cell-free DNA screening showing an increased risk for XXY, with follow-up chromosome analysis showing a 47,XXY karyotype.No family history of reproductive issues, ambiguous genitalia, or consanguinity.Diagnostic Workup: Follow-up studies, including lab work and a pelvic ultrasound, were normal.Chromosomal microarray (CMA) was added following the detection of female genitalia on prenatal ultrasound, which reported a pathogenic Yp11.31 deletion in an XXY chromosome constitution that encompasses SRY.