Intermediate
Technical
IVT
trisomy 21
Pronunciation: TRY-so-mee twenty-one
Chromosomal condition with extra copy of chromosome 21, causing Down syndrome.
Full Definition
A chromosomal condition characterized by the presence of three copies of chromosome 21 instead of the normal two copies, resulting in Down syndrome. This is the most common viable autosomal trisomy, occurring in approximately 1 in 800 births, with risk increasing significantly with maternal age. Trisomy 21 can be detected through various prenatal screening and diagnostic tests, and causes characteristic physical features, intellectual disability, and increased risk of certain medical conditions including heart defects.
Usage
Usage note: Use 'trisomy 21' in medical contexts; 'Down syndrome' in patient communication.
In Context
- "Prenatal testing confirmed trisomy 21 in the developing fetus." — genetic counseling report
- "The screening showed increased risk for trisomy 21 warranting diagnostic testing." — maternal-fetal medicine consultation
Also known as
Down syndrome
trisomy G
Don't confuse with
trisomy 18
trisomy 13