Down Syndrome

Welcome back to my blog, this weeks post is all about Down syndrome!

(Credit: Adobe)

Down syndrome is the most common chromosomal disorder, affecting approximately 1 in 700 newborns. It is also known as Trisomy 21, caused by a third copy of chromosome 21. This disorder affects multiple bodily systems such as the cardiovascular, neurological, and musculoskeletal systems, and causes intellectual disability, characteristic facial features and growth retardation. Some common clinical manifestations and symptoms of Down syndrome can be seen in the image below. 

(Credit: Down syndrome - PMC (nih.gov))

People with Down syndrome have an increased dose of genes on chromosome 21 due to an extra copy, and it has been discovered that just a few of these genes found on this chromosome play an essential role in the phenotype (observable traits) associated with the disorder, for example, DSCR on 21q21.22. It is known that other trisomies are far more common than 21, but Trisomy 21 has a higher survival rate postnatally. 

Down syndrome usually occurs when chromosomes in cell division of reproductive cells do not separate, therefore there are 3 chromosomes instead of 2. The inability to separate may happen in the first round of division or the second, as shown in the image below.

(Credit: Meridian Technical Charter High School)

Trisomy 21 doesn’t have to be caused by a full extra chromosome, in some cases Down syndrome is caused by Robertsonian translocation. This is when an extra arm of chromosome 21 attaches to another chromosome randomly or is inherited from a parent with the translocation, equalling to 2 and a half chromosome 21.

(Credit: Cambridge University Press)

Management is key for those with Down syndrome. Parental education on the disorder and potential clinical manifestations that accompany it is important for the best diagnosis and treatment when complications arise. Also, auditory and visual tests should be undertaken regularly, as they are more prone to impairments. Specialists should also be involved including paediatricians, speech and language therapists, orthopaedic specialists, neurologists, gastroenterologists, and child psychiatrists. Other treatment/management techniques can be seen in the image below. 

(Credit: Very well health)

With the advancements in medicine and health care, the life expectancy for individuals with Down syndrome has improved massively. A study conducted in 1955 showed that only 45% survived their first year of life, and this has steadily been increasing since, as demonstrated by another study done in 2003, where 78% of individuals with Down syndrome and a congenital heart defect survived until the age of 1. 

Thank you for reading! Next, we will be exploring the genetics of Sickle Cell Disease and how the human body may have adapted to use this disease to evade malarial infections.