Human genetic condition
46,XX/46,XY is either a chimeric or mosaic genetic condition characterized by the presence of some cells that express a 46,XX karyotype and some cells that express a 46,XY karyotype in a single human being. While some individuals with this condition may be classified as intersex, others may have typical male or female characteristics.
Types.
Tetragametic chimerism.
The cause of the condition lies in "conception or utero" with the aggregation of two distinct zygotes or blastocysts (one of which expresses 46,XX and the other of which expresses 46,XY) into a single embryo, which subsequently leads to the development of a single individual with two distinct cell lines, instead of a pair of fraternal twins.
In humans, sexual dimorphism is a consequence of the XY sex-determination system. In typical prenatal sex differentiation, the male and female embryo is anatomically identical until week 7 of the pregnancy, when the presence or the absence of the SRY gene on the Y chromosome causes the undetermined gonadal tissue to undergo differentiation and eventually will become either a pair of testes or ovaries respectively. The cells of the developing testes produce Anti-Müllerian hormone, causing the regression of the Müllerian ducts. As individuals with 46,XX/46,XY partially express the SRY gene, the normal process by which an embryo normally develops a phenotypic male or phenotypic female may be significantly affected causing variation will affect in the gonads, the reproductive tract, and the genitals. Despite this, there have been cases of completely normal sex differentiation occurring in 46,XX/46,XY individuals reported in the medical literature. 46,XX/46,XY chimerism can be identified during pregnancy by prenatal screening or in early childhood through genetic testing and direct observation.
Mosaicism.
The cause of this condition happens in early development resulting from a single fertilized zygote's cell line divided into two cell lines; a genome that contains a characterized by the presence of some cells that express a 46,XX karyotype and some cells that express a 46,XY karyotype.
Signs and symptoms.
Physical.
46,XX/46,XY chimeric or mosaic is associated with a wide spectrum of different physical presentations, with cases ranging from having a completely normal male or female phenotype to some cases having ovotesticular syndrome. Due to this variation, genetic testing is the only way to reliably make a diagnosis. 
46,XX/46,XY is possible if there is direct observation of one or more of the following:
There have been no reported cases of both gonads being functional in the same person, the functional tissue is usually the ovarian tissue. A mix of male and female characteristics may emerge at puberty. Some individuals will experience secondary characteristics, such as breast development during puberty in a male phenotype, while others may experience deepening of the voice, secondary hair development, and gynecomastia.
Segmentation of skin (distinct patches of skin) has also been observed. However, this trait is not unique to 46,XX/46,XY chimerism nor mosaicism. It has also been observed in other types of chimerism.
Cognitive.
Individuals with the condition do not experience cognitive impairment.
Genetic mechanism.
46,XX/46,XY is an example of tetragametic chimerism because it requires four gametes – two sperm and two ova.
Diagnosis.
Diagnosing a chimera or mosaic is particularly difficult due to the random distribution of 46,XX and 46,XY cells within the body. In a chimeric, an organ might be made up of a mix of 46,XX and 46,XY, but is made up entirely only one genotype. When that is the case, no abnormalities are noted and other types of tissues need to be analyzed. Blood tests might contain both or red blood cells of different blood types. 
Before birth, ambiguous genitalia might be observed through ultrasound. The karyotype might also be observed through amniocentesis or cord blood sampling.
References.
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