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. 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.
History and exam
Key diagnostic factors
- presence of risk factors
- common physical examination features
- congenital heart disease
- gross motor delay
- language delay
- cognitive disability
- hearing loss
- autism spectrum disorder
Other diagnostic factors
- congenital gastrointestinal disorder
- feeding difficulty
- behavioural difficulties
- advanced maternal age
- previous child with Down's syndrome
- parental karyotype with a translocation
1st investigations to order
- chromosomal karyotype
Investigations to consider
- abdominal x-ray
- hearing test
- thyroid function tests
- vision examination
- dental examination
- developmental evaluation
- psycho-educational evaluation
- total IgA and anti-tissue transglutaminase antibodies
- cervical spine x-rays
- Isolated hypotonia
- Zellweger's syndrome
- Congenital hypothyroidism
- Guidelines on thyroid disorder in children and young people with Down syndrome: surveillance and when to initiate treatment
- Medical care of adults with Down syndrome: a clinical guideline
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