A chromosomal disease that is characterized by flat-looking facial features and weak muscle tone (hypotonia) in infancy and is caused by trisomy of all or a critical portion of chromosome 21 and is associated with intellectual disability. [ url:http://en.wikipedia.org/wiki/Down_syndrome url:http://www.omim.org/entry/190685?search=down%20syndrome&highlight=down%20syndromic%20syndrome url:http://ghr.nlm.nih.gov/condition/down-syndrome url:http://www.nichd.nih.gov/health/topics/down/Pages/default.aspx ]
Synonyms: Downs syndrome, Down's syndrome, Complete trisomy 21 syndrome (disorder), trisomy 21 syndrome, G Trisomy, Down's syndrome - trisomy 21
OMIM mapping confirmed by DO. [SN].