Jérôme Lejeune was a French physician and researcher who studied genetics and developmental disorders. According to the Jérôme Lejeune Foundation, in 1958, Lejeune discovered that the existence of an extra twenty-first chromosome, a condition called Trisomy 21, causes Down Syndrome. Down Syndrome is a condition present in an individual since birth and is characterized by physical and developmental anomalies such as small ears, a short neck, heart defects, and short height as children and adults. Throughout his career, Lejeune also discovered that other developmental disorders, such as cri du chat (cry of the cat) syndrome, were caused by chromosomal abnormalities. Lejeune also used his influence in the scientific community to promote pro-life beliefs, and often met with Pope John Paul II to discuss ethical dilemmas such as abortion of fetuses after detection of chromosomal abnormalities. Lejeune was one of the first researchers to link chromosomal abnormalities to developmental disorders with his discovery of Trisomy 21, leading future researchers to identify more links between the two.

John Langdon Down studied medicine in England in the nineteenth century and was one of the first people to develop a complete description of the disorder that would later be known as Trisomy 21, or Down Syndrome. Down Syndrome is a condition caused by the presence of an extra chromosome, which may cause a person to be born with certain impaired learning abilities and physical features such as a short neck, flattened face, and almond-shaped eyes. In 1866, Down published one of the first accounts to accurately describe people with Down Syndrome, or what he called “Mongolism,” and identify it as a distinct condition. Additionally, Down advocated for people with mental disabilities at a time when their families commonly abandoned them and medical professionals did not prioritize them. He improved the quality of care for people in the centers he worked in and increased their educational opportunities so they would be better prepared to live a normal life. Down brought increased attention to Down Syndrome, leading to the future discovery of the chromosomal anomaly that causes the disorder, and promoting a higher standard of care for people with mental disabilities.

As of 2022, Trisomy 21 is the most common type of trisomy, or a condition where the person has three instead of the normal two copies of one of the chromosomes. Trisomy occurs when abnormal cell division takes place leading to an extra copy of a chromosome. That extra copy of chromosome 21 results in a congenital disorder called Down syndrome, which is characterized by a cluster of specific traits including intellectual disabilities, atypical facial appearance, and a high risk of heart disease. Trisomy 21 changes the way in which a fetus’s brain develops, which accounts for many intellectual disabilities. The United States Centers for Disease Control and Prevention, or CDC, estimates Trisomy 21 occurs approximately once in every 700 human births, averaging about 6,000 live Down syndrome births every year in the US. Down syndrome is a lifelong developmental condition, but there are many resources available to those living with Down syndrome and their families.

The National Association for Down Syndrome, or NADS, is an organization that was founded in 1960 by Kathryn McGee in Chicago, Illinois, to support people with Down syndrome and their families in improving their quality of life. Originally named the Mongoloid Developmental Council, NADS is one of the oldest organizations serving people with Down syndrome and their families in the United States. According to NADS, Down syndrome is a genetic condition that occurs in one in every seven hundred ninety-two people and that causes delays in physical and intellectual development. Members of NADS work to provide information, resources, and access to services and programs for families with Down syndrome, educate the public, address social policy issues and challenges, and facilitate advocacy efforts within the Down syndrome community. For over sixty years, NADS has helped support individuals born with Down syndrome, one of the most common genetic disorders, in the US to find acceptance, develop their capabilities, and work toward independence.

Noninvasive fetal aneuploidy detection technology allows for the detection of fetal genetic conditions, specifically having three chromosomes, a condition called aneuploidy, by analyzing a simple blood sample from the pregnant woman. Dennis Lo and Rossa Chiu researched methods of detection of aneuploidies in the early twenty-first century. Their research has been specifically applied to three trisomies, trisomy twenty-one known as Down syndrome, trisomy eighteen known as Edwards Syndrome, and trisomy thirteen known as Patau Syndrome. Prior to the ability to detect fetal DNA in a pregnant woman’s blood, physicians performed amniocentesis or chorionic villus sampling, two techniques that increase the risk of spontaneous abortion. Noninvasive detection of trisomy twenty-one, eighteen, and thirteen technology allows for a more accurate and safer detection of those conditions than methods available before.

In 2007, Dennis Lo and his colleagues used digital polymerase chain reaction or PCR to detect trisomy 21 in maternal blood, validating the method as a means to detect fetal chromosomal aneuploidies, or an abnormal number of chromosomes in a cell. The team conducted their research at the Chinese University of Hong Kong in Hong Kong, Hong Kong, and at the Boston University in Boston, Massachusetts. Because small amounts of fetal DNA appear in maternal blood during pregnancy, Lo and his team hypothesized that they could detect fetal chromosomal aneuploidy trisomy 21, or Down’s syndrome, in a sample of maternal blood. The group diagnosed Down’s syndrome in unborn fetuses by first taking a maternal blood sample, then amplifying the small amounts of fetal DNA in the maternal blood using digital PCR, and applying two genetic methods to that sample. Lo and his colleagues’ experiment demonstrated the accuracy of a novel, noninvasive method for fetal chromosomal aneuploidy testing that can enable people to make informed decisions about their pregnancies.

Subscribe to Down syndrome