Down syndrome results from the presence of an extra copy of chromosome 21 meaning that these patients have three copies of this chromosome (trisomy 21). Down syndrome is the leading cause of intellectual disability and is the most common genetic alteration in humans. Prevalence is estimated at 1 in 750-800 births. The average life expectancy is over 50 years.
The risk of having a child affected by this syndrome increases with maternal age, especially after 35 years of age.
- 1/385 risk at age 35 years
- 1/106 at age 40 years
- 1/30 at age 45 years
Most frequent clinical findings in patients with Down syndrome:
- Intellectual deficit
- Muscular hypotonia (lack of muscle strength)
- Heart problems
- Small stature
- Early aging
- Infertility in men and a severe decrease in fertility in women
Ds-int.org – Down Syndrome International