Abstract
Klinefelter syndrome (KS) is a common chromosomal abnormality in males, usually presenting as a 47,XXY karyotype and often underdiagnosed. Rarely, KS occurs as mosaic 46,XX/47,XXY. At the same time, ovotesticular disorder of sex development (OT-DSD) is also a rare condition in which both ovarian and testicular structures are present in the same individual, often associated with a 46,XX karyotype. The combination of mosaic 46,XX/47,XXY with OT-DSD is scarce. Herein, we report a new case of a six-month-old infant with unilateral OT-DSD and a 46,XX/47,XXY mosaic karyotype who presented with atypical genitalia at birth. On examination, the external genitalia showed asymmetry of the labioscrotal folds, an empty right fold, a 2.5 cm phallic structure, and a perineal urethral meatus. Imaging studies revealed a uterus and a vaginal cavity, as well as an ovotestis on the left side and an ovarian remnant on the right side. An unexpected increase in testosterone level was observed. Cytogenetics analysis confirmed a mosaic karyotype with 54% of 46,XX and 46% 47,XXY cells. Molecular genetic analysis revealed no mutations in the genes involved in gonadal development. These findings are discussed and the clinical characteristics of the reported cases of 46,XX/47,XXY with OT-DSD are summarized. In conclusion, atypical genitalia leads to the early diagnosis of the rare 46,XX/47,XXY mosaicism with OT-DSD. Mosaicism should be considered in all cryptorchidism cases. Persistent Müllerian structures were common, and the nearly male phenotype of the external genitalia led parents to prefer the male sex of rearing.