True hermaphroditism, sometimes referred to as ovotesticular syndrome, is an intersex condition in which an individual is born with both ovarian and testicular tissue. Commonly, one or both gonads is an ovotestis containing both types of tissue. Although it is similar in some ways to mixed gonadal dysgenesis, the conditions can be distinguished histologically. Symptoms Gynecomastia (present in 75% of cases.) History The first medical attempts to document cases appeared in the 16th century. Up until the Late Middle Ages individuals with these conditions were viewed as monsters. Causes There are several ways in which this may occur. It can be caused by the division of one ovum, followed by fertilization of each haploid ovum and fusion of the two zygotes early in development. Alternately, an ovum can be fertilized by two sperm followed by trisomic rescue in one or more daughter cells. Two ova fertilized by two sperm cells will occasionally fuse to form a tetragametic chimera, if one male zygote and one female zygote fuse. It can be associated with a mutation in the SRY gene. Karyotypes In ovotesticular syndrome, XX is the most common (55-80% of cases); most individuals with this form are SRY negative. Next most common are XX/XY (20-30% of cases) and XY (5-15% of cases), with the remainder being a variety of other chromosomal anomalies and mosaicisms. Some degree of mosaicism is present in about 25%. Encountered karyotypes include 46XX/46XY, or 46XX/47XXY or XX & XY with SRY mutations, mixed chromosomal anomalies or hormone deficiency/excess disorders, 47XXY. Less than 1% have XX/XY chimerism. Prevalence True hermaphroditism represents 5% of all sex disorder differentiations. The exact number of confirmed cases is uncertain, but by 1991 approximately 500 cases had been confirmed. It has also been estimated that more than 525 have been documented. Fertility The gonad most likely to function is the ovary. The ovotestes show evidence of ovulation in 50% of cases. Spermatogenesis has only been observed in solitary testes and not in the testicular portions of ovotestes. According to a 1994 study, spermatogenesis has only been proven in two cases. One of the two cases, having XX,46/XY,46 mixture had fathered a child. It has been estimated that 80% of cases could be fertile as females with the right surgeries. Documented cases of fertility There are extremely rare cases of fertility in "truly hermaphroditic" humans. In 1994 a study on 283 cases found 21