Are there different types of Down syndrome?

Are there different types of Down syndrome?

Yes, there are three types of Down syndrome. They are:

• Trisomy 21: The term “trisomy” means having an extra copy of a chromosome. The most common type of Down syndrome, trisomy 21, occurs when a developing baby has three copies of chromosome 21 in every cell instead of the typical two copies. This type makes up 95% of the cases.
• Translocation: In this type of Down syndrome, there is an extra full or partial amount of chromosome 21 attached to another chromosome. Translocation accounts for 4% of the cases.
• Mosaicism: In the rarest type (only 1%) of Down syndrome, some cells contain the usual 46 chromosomes, and some contain 47. The extra chromosome in these cases is chromosome 21.