ESPE Abstracts

Introduction: 45,X/46,XY mosaicism is a rare sex chromosome abnormality. The aim of this study is to provide outcomes, namely growth, comorbidities and gonadal function in patients with 45,X/46,XY mosaicism.

Methods: This was a retrospective, longitudinal study conducted from January 2006 to January 2021 at a tertiary pediatric endocrine referral center. Patients' clinical presentation, karyotypes, height, hormonal profiles, imaging and histologic findings of the gonads were evaluated. Phenotypes were scored using external masculinization scores (EMS).

Results: A total of 12 patients (8 boys, 4 girls) with 45,X/46,XY mosaicism and its variants were included. 11 out of 12 patients presented with ambiguous genitalia. Median height SD score was -2.62 (range, -3.26 to -2.0) for females and -0.46 (range, 0.13 to -1.7) for males, both below genetic potential. 25% of patients had other abnormalities – cardiac and renal abnormality Males in our cohort were undervirilized as the median EMS score was 4.5 [3.75 – 7.25]. During the course of follow up two patients underwent gender change. Two male patients had testicular microlithiasis. Mullerian duct remnants were identified 66% of the time. Histology of 14 gonads was available from patients who had undergone a gonadectomy or gonadal biopsy. All tissue samples from patients revealed abnormal gonadal histology. All intrabdominal gonads were streak or dysgenetic testicular tissue.

Conclusions: The 45,X/46,XY phenotype varies widely. Short stature and 45,X/46,XY mosaicism are associated. Management of each patient should be individualized according to the clinical assessment.