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updated: July 2, 2022


Mosaicism refers to the presence of cells in a person that have a different genome from the body’s other cells. This difference could be due to a specific genomic variant, for example, or the addition or loss of a chromosome. The condition can stem from a genetic error that occurs after fertilization of an egg, during very early embryo development, or it could occur later in development. Mosaicism can affect any type of cell and does not always cause disease.