Mosaic Down Syndrome
Type of disease: Rare conditions
Mosaic Down syndrome is a form of down syndrome where only some of the cells have an extra copy of the 21st chromosome, while others have the normal number of all of the chromosomes. (For more information, see Down syndrome). 2-4% of people with Down syndrome have mosaic Down syndrome. Little research has been done on mosaic Down syndrome, so some individuals who have been diagnosed with Down syndrome may actually have mosaic Down syndrome. Symptoms of mosaic Down syndrome depend on which and how many cells have extra copies of chromosome 21, but may include intellectual disability and slow speech or motor development. Mosaic down syndrome can only be diagnosed through a blood test, and most children are diagnosed between 1-4 years of age.