The term “mosaicism” describes a situation in which different cells in the same individual have different numbers or arrangements of chromosomes. It is called “mosaicism” because, in a way, the cells of the body are similar to the tiles of a mosaic. In a mosaic piece of art, each tile is different. They have different shapes and colors. The tiles are fitted together to make a whole picture.
If a person has mosaicism, their cells are like the tiles of a mosaic. Taken together, the different tiles of the mosaic form the whole picture, similar to the way the cells form the whole body. Just as the tiles of a mosaic have different shapes and colors, the cells of the body have different numbers or arrangements of chromosomes. For example, if an individual has mosaic trisomy 18, this means that some of the cells have three copies of chromosome 18 while other cells have two copies of chromosome 18.
For a more comprehensive understanding of other conditions, please refer to the detailed information provided in the Mosaicism handouts that are downloadable and printable items.
For Additional Information:
The information provided here is general information based on the literature as well as the experiences in the Chromosome 18 Clinical Research Center. As always, we recommend talking with a clinical geneticist or genetic counselor to learn more about the specific chromosome change that has been identified in your family. You can locate a genetics provider at one of these sites: