People with mosaic Down syndrome can manifest all, some or none of the symptoms of the more common form of Down syndrome, including short stature, slanted eyes, intellectual disability and heart defects. Due to the way mosaic Down syndrome develops in the child's body, the effects of mosaicism are complex and difficult to predict, reports Stanford Children's Health.
Down syndrome is caused by the accidental duplication of a single chromosome, number 21, at or prior to the single-cell stage of development. When this occurs, every cell in the body is trisomatic. In mosaic Down syndrome, the duplication occurs somewhat later than the single-cell stage, and only the cells directly descended from the original abnormal cell are trisomatic. According to Stanford Children's Health, this can lead to vastly different presentations of symptoms as the concentration of trisomatic cells varies from one type of tissue to another. The total percentage of affected cells varies as well, which can result in a patient with a full presentation of Down syndrome or no presentation of symptoms at all. Some patients fall along the spectrum between the two, with some degree of mental disability, physical handicap or other health problem.
According to WebMD, Down syndrome can present up to 50 symptoms. Some symptoms include weak muscles, shorter arms and legs, irregular teeth and mouth, hypothyroidism, and celiac disease. Patients with mosaic Down syndrome are subject to any of these, as are people diagnosed with the more common form of Down syndrome.