Down's syndrome

Down's syndrome is the most common genetic cause of cognitive or intellectual disability, with a prevalence of 1 in 691 births.

Characteristic physical features include brachycephaly with a flat occiput; epicanthal folds and upslanting palpebral fissures; Brushfield spots in the iris; low nasal bridge; low-set ears; broad neck; and small hands with transverse crease.

Individuals with Down's syndrome have a higher frequency of congenital and acquired medical conditions, including congenital heart defects and audiological, vision, gastrointestinal, haematological, and thyroid issues.

Global developmental delay is common; however, cognitive abilities vary greatly, with IQ ranging from mild to moderate intellectual disability. Behavioural difficulties, if present, tend to be age-related (e.g., hyperactivity and impulsiveness in younger children; withdrawal and anxiety in older adolescents). Screening and clinical observation of symptoms suggestive of autism spectrum disorder is recommended.

Early interventional therapies (e.g., speech therapy, physiotherapy, occupational therapy) and individualised educational programmes/resources are essential to maximise the potential of a person with Down's syndrome.

Down's syndrome (DS), or trisomy 21, is the most common genetic form of intellectual disability, occurring in 1 in 691 births.[1]Parker SE, Mai CT, Canfield MA, et al. Updated National Birth Prevalence estimates for selected birth defects in the United States, 2004-2006. Birth Defects Res A Clin Mol Teratol. 2010;88:1008-16. http://www.ncbi.nlm.nih.gov/pubmed/20878909?tool=bestpractice.com In addition to having characteristic physical features, short stature, and hypotonia, individuals with DS have a distinctive cognitive and behavioural profile. They also have a higher frequency of associated medical conditions, including congenital heart defects, and gastrointestinal, thyroid, haematological, audiological, and visual abnormalities.