(5) A rare case of 45X/46XY mosaic Turner syndrome in a neonate

Background: Ambiguous genitalia in a newborn can be challenging to diagnose and manage. We present a case of a 2-month-old infant with atypical genitalia and genetic (45X/46XY) mosaicism.

Case: A healthy infant, delivered after an uncomplicated pregnancy at 39 weeks’ gestation was observed to have ambiguous genitalia. Prenatal cell-free DNA showed 40% risk for Turner’s syndrome. A physical exam demonstrated an enlarged clitoris and fusion of the labioscrotal fold with a palpable mass in the left inguinal canal. Pelvic ultrasound showed a left inguinal testicle, no obvious ovarian tissue, and the presence of rudimentary Mullerian structures. Serum hormonal evaluation at 6 weeks of life included a testosterone of 118.3, ng/dL, inhibin B of 139 pg/ml, AMH of 32 ng/ml, and dihydrotestosterone level of 30 ng/dL suggesting testicular function . Estradiol levels were 3 pg/mL. Cytogenetics revealed 45X/46XY mosaicism with an SRY gene. Genitogram demonstrated a urogenital sinus. Concern was raised for potential dysgenetic gonads, which carry a risk for malignancy and a shared decision was made to pursue an exam under anesthesia and diagnostic laparoscopy to assess gonads and mullerian structures. Surgical findings included a short urogenital sinus and a 1 cm vaginal canal. A normal-appearing single cervix was visualized, and the left testicle was identified in the inguinal canal. A right-sided streak gonad (Figure 1A, black arrow), fallopian tube (Figure 1B, green arrow) and small right hemi-uterus (Figure 1D, Pink arrow) were visualized. A left inguinal orchiopexy, left inguinal hernia repair (Figure 1C) and right gonadectomy and salpingectomy (Figure 1) was performed. Pathology showed benign ovarian stroma, with rete-testes like structures.

We describe one of the few cases of a neonatal diagnosis of Mosiac Turner’s syndrome with the presence of both testicular and Mullerian tissue. The diagnostic challenge of such cases is that imaging modalities are limited, and surgical exploration is often necessary for definitive phenotype analysis. Furthermore, it is important to counsel parents on the potential outcomes and encourage shared decision-making to consider future options for the child’s sex of rearing whilst reducing the risk of possible malignancies.

Comments: -We highlight a rare case of neonatal 45X/46XY Mosaic Turner’s syndrome with surgical findings of a normal cervix, urogenital sinus, a left semi-descended testicle, right streak gonad and fallopian tube, and hemi-uterus
-We highlight the role of shared decision-making when managing rare, complex presentations of mosaic Turner’s, including reducing the risk of gonadoblastomas