(also known as Trisomy 21, T21).

This syndrome was initially described by Dr John Langdon Down, a London based Physician in 1866. It is the most common pattern of malformation in humans with a birth incidence of 1:660.

The vast majority are due to the inheritance of an additional chromosome 21 at the time of conception.

 

Features of Down Syndrome

‘Mongoloid’ facial appearance.
Cardiac abnormalities – approximately 50%
Intellectual disability – leading to mild/moderate cognitive delay – possible autistic spectrum
Weak muscle tone
Digestive abnormalities – oesophageal reflux, coeliac disease.
Underactive thyroid in 15%
Hearing, speech and visual problems – language delay, attention problems.
Obsessive/compulsive behaviour, stubbornness and tantrums
Some dev
Small percentage develop leukaemia
Gradual decline in thinking ability with age, usually around age 50, developing Alzheimers in approximately 50%.

Pregnancies affected by Down Syndrome increases with maternal age.