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.
True hermaphroditism
XY gonadal dysgenesis
Gonadal dysgenesis
Androgen-induced hermaphroditism
XX gonadal dysgenesis
Pseudohermaphroditism
Müllerian agenesis
45,X/46,XY mosaicism