March 21: World Down Syndrome Day

Céline Arétin, culture, women's issues and environment correspondent, March 21, 2025

What is Down syndrome?

Down syndrome, also called trisomy 21, is a genetic condition caused by the presence of an extra chromosome 21. This abnormality results in 47 chromosomes instead of 46 in the individual's cells. It's estimated that about 1 in 700 births is affected by trisomy 21, making it one of the most common chromosomal abnormalities in the world, with nearly 65,000 people affected in France. This genetic condition affects both boys and girls, but the risk of having an affected child increases with the mother's age. At age 20, this risk is about 1 in 2,000, while at age 40, it rises to 1 in 100.

Daily challenges faced by people with trisomy 21

Medically, people with trisomy 21 are more prone to health issues such as congenital heart conditions, hearing impairments or thyroid disorders. About 40 to 50% of children born with trisomy 21 are born with a heart defect, sometimes requiring surgery within the first months of life. In addition, nearly 15% of affected children develop digestive disorders, such as celiac disease or gastroesophageal reflux. Despite these challenges, nearly 70% of children with trisomy 21 attend mainstream schools with appropriate support.

Scientific research on Down syndrome

In 2013, researchers at the University of Massachusetts succeeded in silencing the third chromosome 21 in human cells by inserting a gene called XIST. In France, the Jérôme Lejeune Institute is working on improving cognitive abilities through clinical trials involving molecules such as Epigallocatechin Gallate (EGCG), an antioxidant extracted from green tea that may improve memory and learning. In the United States, Boston Children's Hospital is conducting studies on the molecule PTZ (Pentylenetetrazole), which has shown promising results for improving brain plasticity. Medically, progress has been made in treating congenital heart defects, with early interventions increasing life expectancy, now estimated at around 60 years on average, compared to 25 years in the 1980s.