Gonadoblastoma presenting as isosexual precocious puberty in a genetic female.

A 6 1/2-year-old female with pseudoprecocious puberty was found to have a gonadoblastoma. Her karyotype was 46, XX; serum estradiol level was markedly elevated; and androgens were within the range of normal. The importance of the Y chromosome and dysgenetic gonad in the predisposition to development of a gonadoblastoma is reviewed. A further categorization of gonadoblastomas based on the presence or absence of the Y chromosome is suggested.