Mosaic trisomy 8 is a chromosomal abnormality that can affect many parts of the body. In individuals with Mosaic trisomy 8, some of the body's cells have three copies of chromosome 8 (trisomy), while other cells have the usual two copies of this chromosome. The signs and symptoms vary, but may include distinctive facial features; intellectual disability; and joint, kidney, cardiac, and skeletal abnormalities. Males are more frequently affected than females. Most cases are not inherited; it often occurs sporadically as a random event during the formation of the reproductive cells (egg and sperm). Diagnosis may be based on analysis of chromosomes via genetic testing, such as karyotype.