Ovotesticular Disorder of Sex Development with 46,XX/47,XXY Mosaicism: Challenges in Diagnosis, Gender Assignment, Gonadal Preservation, and Long-Term Oncologic Surveillance: A Case Report

Introduction Ovotesticular disorder of sex development (DSD) is a rare condition, most commonly associated with a 46,XX karyotype. Mosaic karyotypes such as 46,XX/47,XXY are extremely uncommon and pose unique diagnostic and management challenges, particularly regarding gender assignment, gonadal preservation, and long-term surveillance. Case Presentation We report a patient with 46,XX/47,XXY mosaicism who presented at birth with ambiguous genitalia. Imaging and histology revealed a right testis, a left ovary, and both Müllerian and Wolffian structures. Following multidisciplinary evaluation and parental counseling, the child was raised as male and underwent staged masculinizing genitoplasty, including hysterectomy, vaginectomy, and hypospadias repair. At age 11, rising estradiol levels and gynecomastia led to the discovery of hormonally active ovarian tissue within the right gonad. Gonad-sparing reoperation was performed to remove the ovarian component while preserving testicular tissue. Histology confirmed the presence of follicles and intact seminiferous tubules. Despite favorable pathology, elevated gonadotropins indicated primary gonadal failure. Discussion This case highlights the diagnostic complexity and long-term management challenges in ovotesticular DSD with sex chromosome mosaicism. Even after early surgical intervention, residual ovarian tissue may become hormonally active at puberty. Lifelong multidisciplinary follow-up is essential to monitor endocrine function, psychosocial development, and oncologic risk in such patients. Conclusion Ovotesticular DSD with 46,XX/47,XXY mosaicism requires individualized, long-term care. This case underscores the importance of vigilant surveillance beyond early childhood, as hormonally active gonadal tissue may emerge later in development. Timely re-evaluation and organ-preserving interventions can support both endocrine stability and psychosocial well-being.