Catamenial Hematuria in Mixed Gonadal Dysgenesis (45,X/46,XY): A Case Report of a Rare Presentation.

Mixed gonadal dysgenesis (MGD) is a rare disorder of sex development (DSD) associated with 45,X/46,XY mosaicism and variable phenotypic presentation. Mullerian remnants may persist but are typically non-functional. We report a 16-year-old phenotypic male with hypospadias and a unilateral undescended testis with prior resection of a streak gonad containing fallopian tube structures, who presented with cyclical hematuria and lower abdominal pain. Imaging suggested a Müllerian duct cyst. Diagnostic laparoscopy and cystoscopy revealed a cystic structure communicating with the posterior urethra, initially mimicking a diverticulum. Surgical excision was performed, and histopathology demonstrated uterine tissue with proliferative endometrium. The symptoms were attributed to catamenial bleeding from functional Müllerian tissue. This case highlights a rare presentation of MGD and emphasizes the importance of considering Müllerian remnants in phenotypic males with cyclical hematuria.