A genetic (inborn or inherited) disorder, leading to challenges with cognition (thinking) and learning as well as some unique physical, medical and developmental issues.
Trisomy 21 – 3 copies (instead of 2) on chromosome 21 ("tri" means "3" and "somy" refers to "chromosomes"). We all have 26 pairs ("body") chromosomes and "1" pair ("sex") chromosomes – either XX for femal and XY for males.
It's the commonest inherited cause of intellectual disabilities. Researchers have established that the likelihood that a reproductive cell will contain an extra copy of chromosome 21 increases dramatically as a woman ages.
| Mothers Age | Incidence of Down Syndrome |
| Under 30 | Less than 1 in 1,000 |
| 30 | 1 in 900 |
| 35 | 1 in 400 |
| 36 | 1 in 300 |
| 37 | 1 in 230 |
| 38 | 1 in 180 |
| 39 | 1 in 135 |
| 40 | 1 in 105 |
| 42 | 1 in 60 |
| 44 | 1 in 35 |
| 46 | 1 in 20 |
| 48 | 1 in 16 |
| 49 | 1 in 12 |
All have resemblance or physical features in common, which makes them easily recognizable: flattened facial profile, upward slant eyes, low muscle tone (this makes them appear open-mouthed as well) and a single deep crease across the centre of 1 or both palms.
Medical Issues, like Congenital Heart Disease. (>80%) abnormalities of the gastrointestinal system, hearing and / or visual impairment, some type/s of hormonal problems e.g. thyroid, intellectual disabilities (mild-moderate-severe).
May not need all types of therapies during life span: