Chimerism is a very rare genetic defect that occurs when a person carries more than 1 type of DNA in their body.
Generally, this change does not cause symptoms, but there may be changes such as asymmetries and deformity in the body of the carrier or, in rarer cases, hermaphroditism.
This situation is different from the mosaicism, in which the person may present genetic alterations, which are due to a mutation in the genetic material. Learn what is and how to identify mosaicism.
Chimerism can happen in two ways:
1. Natural or genetic chimerism
It is the classic form of chimerism, which originates when 2 or more embryos merge into one. Thus, the baby will be born with 2 or more different types of genetic material, as shown in the following figure:
A person with this change may have 2 or more different types of DNA in the body, and if the DNAs are of the same sex, there are usually no serious consequences for the person's life, and may or may not show some signs, such as asymmetries of the body, of skin color or pain eyes, for example.
However, if they are of different sexes, the person will be born hermaphrodite. Understand what is and how to identify hermaphroditism.
2. Artificial Chimerism
It happens when the person receives an organ transplant, such as the bone marrow, and the organ's DNA is incorporated into the tissues of the person's body and can be detected through genetic testing. This situation is beneficial, since this means that the body of the transplanted person accepted the organ well, reducing the risks of rejection.
Another form that has been demonstrated of chimerism is known as microchimerism, and it happens during normal gestation, in which some cells of the mother, or even, of a twin baby, can be passed from one to the other, being that the permanence of these cells can last for years.
There is also the microchemistry that happens through the transfusion of blood, in which the DNA of transfused blood cells can last for a few days in the circulation of the recipient.
Although this type of chimerism is not shown to cause health damage, some research has shown that it may be associated with the development of autoimmune diseases.
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