Introduction

Down syndrome, also known as Trisomy 21, is a chromosomal anomaly characterized by the presence of three chromosomes instead of two on the twenty-first pair of the twenty-three pairs of human chromosomes.

A Chromosomal Error at the Origin

Humans have 46 chromosomes, carriers of DNA, inherited equally from both parents. Down syndrome originates from a genetic anomaly: an extra chromosome on the 21st pair. Instead of 46 chromosomes, an affected person has 47. This difference occurs at conception, usually due to an error during the formation of reproductive cells. According to a United Nations report, approximately 3,000 to 5,000 children are born each year worldwide with this chromosomal anomaly.

Risk Factors and Diagnostic Methods

Experts estimate that the risk of Trisomy 21 increases with maternal age. Women aged 35 or older have a higher likelihood of giving birth to a child with Down syndrome. Prenatal screening during the early months of pregnancy is essential to assess this risk. First-trimester obstetric ultrasound, particularly the measurement of nuchal translucency (the distance between the skin of the neck and the fetal spine), can detect certain anomalies. When combined with maternal blood tests, this measurement helps estimate the probability of Trisomy 21. In cases of suspicion, amniocentesis may be performed, involving the extraction of a small amount of amniotic fluid to analyze the fetus’s chromosomes. In the 1960s, the life expectancy of a person with Down syndrome did not exceed 10 years. Today, thanks to medical advances, it can reach 60 years. While Trisomy 21 cannot be cured—since the extra chromosome cannot be removed or altered—scientific progress and specialized care significantly improve quality of life. Individuals affected require lifelong medical and educational support, which is often costly but essential.

Consequences of Trisomy 21

People with Trisomy 21 often present mild to moderate intellectual delays, growth issues, as well as heart or hearing problems. They also display certain physical traits: short stature, slightly smaller head, flattened face, almond-shaped eyes, short neck, small hands, and low muscle tone.

Conclusion

Long considered a disease, Trisomy 21 is now better understood as a genetic difference that requires empathy and appropriate support. While science has extended the life expectancy of those affected, real progress lies in recognizing their abilities and role within society. Beyond medical challenges, the focus is now on inclusion, respect, and dignity. Understanding Trisomy 21 means accepting that human diversity is a strength and that every individual, regardless of genetic makeup, deserves a full life and to be seen with hope.