Down Syndrome - Causes
Down syndrome, also known as trisomy 21, is a genetic disorder.
Down syndrome is a genetic condition that results when there is an extra copy of a specific chromosome, chromosome 21.
It is not an illness but a term that describes the features resulting from this change.
The extra chromosome can affect the physical features, intellect, and overall development of an individual.
It also increases the likelihood of some health problems.
Causes
Down syndrome happens when there is an extra copy of genetic material on all or part of the 21st chromosome.
Every cell in the body contains genes that are grouped along chromosomes in the cell's nucleus. There are normally 46 chromosomes in each cell, 23 inherited from the mother and 23 from the father.
When some or all of a person's cells have an extra full, or partial, copy of chromosome 21, the result is Down syndrome.
Characteristics
People with Down syndrome often have distinct physical features, unique health issues, and variability in cognitive development.
Physical features
Physical characteristics include:
eyes that have an upward slant, oblique fissures, epicanthic skin folds on the inner corner, and white spots on the iris
low muscle tone
small stature and short neck
flat nasal bridge
single, deep creases across the center of the palm
protruding tongue
large space between large and second toe
a single flexion furrow of the fifth finger
Developmental delays
Individuals with Down syndrome usually have cognitive development profiles that suggest mild to moderate intellectual disability. However, cognitive development and intellectual ability are highly variable.
Children with Down syndrome often reach developmental milestones later than their peers.
There may be a delay in acquiring speech. A child may need speech therapy to help them gain expressive language.
Fine motor skills may also be delayed. They can take time to develop after gross motor skills have been acquired.
On average, a child with Down syndrome will:
sit at 11 months
crawl at 17 months
walk at 26 months
There may also be problems with attention, a tendency to make poor judgments, and impulsive behavior.
However, people with Down syndrome can attend school and become active, working members of the community.
Health issues
Sometimes, there are general health problems that can affect any organ system or bodily function. Around half of all people with Down syndrome have a congenital heart defect.
There may also be a higher risk of:
respiratory problems
hearing difficulties
Alzheimer's disease
childhood leukemia
epilepsy
thyroid conditions
However, there also appears to be a lower risk of hardening of the arteries, diabetic retinopathy, and most kinds of cancer.
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