The mission of the Jerome Lejeune Foundation USA is to provide research, care, and advocacy for people with genetic intellectual disabilities. This is achieved by conducting, promoting, and funding therapeutically oriented research; by assisting in the development of healthcare services; and by serving as an advocate in a spirit of respect for the dignity of all human persons. Created in 1996 in Paris and in 2012 in the United States, the Jerome Lejeune Foundation is registered with the Internal Revenue Service as a 501(c)(3) nonprofit corporation.

While many people remember Jerome Lejeune for his discovery of the genetic cause of Down syndrome, or trisomy 21, few know that he also identified trisomies on chromosomes 8 and 9, described 18q- syndrome, and discovered that cri du chat (cry of the cat) syndrome is caused by a missing segment of chromosome 5. He is appropriately called the "Father of Modern Genetics." The Jerome Lejeune Foundation is an international foundation with offices in France and the U.S. It is the world's largest private funder of research into genetic intellectual disabilities.