Mixed gonadal dysgenesis.

Mixed gonadal dysgenesis is an intersex syndrome characterized by a unilateral streak gonad, persistent müllerian duct structures and ambiguous genitalia. These patients are chromatin negative and exhibit XO/XY mosaicism. The disorder probably results from a cytogenetic error that occurs early in embryogenesis. These patients usually are reared as female subjects but masculinity begins at puberty because of the qualitatively and quantitatively normal testicular androgenic function. The patients are diagnosed on the basis of a Y chromosomal component and the presence of a unilateral testis and contralateral streak gonad at the time of exploratory laparotomy. The testis and the streak gonad should be removed because of the potential development of a gonadoblastoma and the virilization that occurs at puberty.