mosaicism
(moh-ZAY-ih-SIH-zum)
A condition in which some cells or tissues in a person’s body have a different genetic or chromosomal makeup than those in the rest of the body. Mosaicism is caused by a genetic change that occurs during cell division. This can happen during embryo development or after birth. Mosaicism can affect a large number of cells or only a few cells. It may or may not cause disease.