Down syndrome

Down syndrome is a genetic caused developmental disability that occurs when there is a partial or fully extra chromosome in chromosome 21, as there are intended to be 23 pairs of chromosomes, half coming from the mother, and half from the father. While this may already be a well known fact around Down syndrome, there are also three different ways in which Down syndrome may happen: Trisomy 21, Mosaic Down syndrome, and translocation Down syndrome. Let’s break down how each of these genetic variations are defined. 

Trisomy 21: This is by far the most common way of Down syndrome occurring in an individual. This is when an individual has 3 copies of chromosome 21 instead of the usual 2.

Mosaic Down syndrome: A less common form of Down syndrome that is caused by an extra copy of chromosome 21 in only some, but not all, cells.

Translocation Down syndrome: This is also a rare form of Down syndrome that occurs when a portion of chromosome 21 is attached to another chromosome. They will have the typical pair of chromosome 21 while also having extra genetic material from chromosome 21 in other chromosomes. 

There are roughly 6,000 babies born with Down syndrome each year. In addition, older mothers are more likely to have a child with Down syndrome than younger mothers. In essence, the older a mother gets, the greater probability of having a child with Down syndrome becomes, although it still only affects about 1 in 700 children born. Mothers aged 40 or up have 3 times the chance of mothers aged 34-39, and 6 times the chance of mothers in their 20s to have a child with Down syndrome. 

Myths

Myth 1: all individuals with Down syndrome have a severe cognitive disability. 

What’s true is that most individuals with Down syndrome have a mild to moderate intellectual disability. It’s important to emphasize that Down syndrome affects each individual differently. 

Myth 2: Only white people can have Down syndrome.

While Down syndrome occurs the most often in white individuals (67%), it also occurs in Hispanic (16%), Black (13%), Asian or Pacific (3%), and American Indian individuals (1%).  

Myth 3: All adults with Down syndrome are childlike 

This is not true, as most individuals with Down syndrome have mild to moderate intellectual disability. Adults should be treated as adults, regardless of if they have Down syndrome or not. 

Individuals with Down syndrome have an increased risk of obesity, dementia, heart defects, gastrointestinal defects, immune disorders, sleep apnea, and spinal problems, than someone without Down syndrome. In addition, individuals with Down syndrome today have a life expectancy of 60 years old, compared to age 25 in 1983.  

To read more about the history of down syndrome, you can click the button below.

John Langdon Down and the History of Down syndrome