Down syndrome (Ds) is the most common chromosomal condition, in which an individual has a full or partial extra copy of the 21st chromosome. This additional genetic material alters the course of development and causes the characteristics associated with Down syndrome. There are approximately 400,000 people living with Down syndrome in the USA alone. Down syndrome does not discriminate, it occurs in people of all races and economic levels.
Peter was prenatally diagnosed with Down syndrome. Markers were first caught in a routine ultrasound, and confirmation was obtained through an amniocentesis. Looking at our little dude swimming around on the screen during the ultrasound, he looked like a little teddy bear with short little arms and legs. During our pregnancy journey, he fondly became Baby Bear. People around the world prayed for Baby Bear! As he grew bigger, the nickname transitioned to Peter Bear. A name he still proudly wears today!
Why is it called Down syndrome?
For many who know individuals with Down syndrome, the name just doesn’t make sense. Down? Really?!
The label “Down syndrome” is not meant to describe those with the condition as being “down”. As with many medical conditions, it is named after a physician who described the condition.
In the 1860’s, Dr. John Langdon Down published a paper describing a certain subset of his patients at the Royal Earlswood Asylum for Idiots (as it was called at that time). In that era when Charles Darwin and the theory of evolution were new, Dr. Down theorized that these patients were a “regression” in the evolution of man. Their physical appearance reminded Dr. Down of people from Mongolia, so he termed the condition “Mongolian idiocy.” The condition was known by this name, or shortened to referring to the individuals with the condition as “Mongoloids” or “Mongols”.
In 1961, the medical journal Lancet ran a letter from noted geneticists calling for a re-naming of the condition. The editor selected “Down’s syndrome” and the World Health Organization (WHO) confirmed that description for the condition in 1965. And, that is how “Mongolian idiocy” became known as “Down’s syndrome”, and now commonly referred to as “Down syndrome” (losing the ‘s, since Dr. Down didn’t have the syndrome).
Interestingly, Dr. Down passed in 1896, never meeting his grandson and namesake. The younger John Langdon Down, was born in 1905 with Down syndrome, and grew to be a much loved member of the family. He died in the ancestral home at age 65.
Functional levels?
I often get asked what degree of Down syndrome Peter has, but the question is really asking about his “function” level. Is he “high functioning” or “low functioning”?
Down syndrome is NOT a spectrum on which individuals having varying degrees of Down syndrome that then fall into “functioning” levels.
As with all people, individuals with Down syndrome have different strengths and weakness, which influence their ability to succeed in different areas. In addition, individuals may have other conditions that influence their ability in different environments. While some disorders occur more frequently in individuals with Down syndrome, they are not limited to these individuals.
For example, Peter has various conditions, including “Speech Apraxia”, that have limited his ability to communicate verbally. Most children his age, with Down syndrome, are able to more clearly articulate and string words together than he can now. Peter receives Speech Therapy to help him continue to develop communication.
So, are there “types” of Down syndrome?
Yes, there are three different types of Down syndrome: Standard Trisomy 21, Translocation, and Mosaicism.
Standard Trisomy 21/Nondisjunction is when the extra chromosome 21 in every cell. An estimated 95% of all Down syndrome cases is Standard Trisomy 21. This is the form of Down syndrome Peter was diagnosed with prenatally.
Translocationis caused when a piece of chromosome 21 is located on another chromosome such as chromosome 14. The person with Translocation Trisomy 21 will have 46 chromosomes but will have the genetic material of 47 chromosomes. The person with Translocation Trisomy 21 will exhibit all the same characteristics of a person with Standard Trisomy 21 since they have three copies of chromosome 21. Translocation occurs in an estimated 3% of cases of Down syndrome.
Mosaicismis when a person has a mix of cells, some containing 46 chromosomes and some containing 47 chromosomes. This occurs either because: a) The person received 46 chromosomes at fertilization but somewhere during early cell division the chromosome 21 cell pairs failed to split creating a cell with 47 chromosomes and a cell with 45 chromosomes. The cell with 45 chromosomes can not survive but the cell with 47 chromosomes will continue to divide. All cells that come from this cell will contain 47 chromosomes. b) The person received 47 chromosomes at fertilization but later during cell division the extra chromosome is lost. Mosaicism occurs in an estimated 2% of cases of Down syndrome. A person with Mosaic Down syndrome may exhibit all, some, or none of the characteristics of Down syndrome depending on the percent of cells carrying the extra chromosome and where these cells are located.