A century after Down syndrome was first described, scientists discovered that the root cause of this disorder is a condition called trisomy 21. What strides ... slant to the eye, a flat nose ...

Down Syndrome, known as Trisomy 21, is a genetic disorder caused by an extra chromosome 21. It affects facial appearance, ...

Medically reviewed by Brigid Dwyer, MD Mosaic Down syndrome is a variant of Down syndrome. Down syndrome is a congenital ...