Rett Syndrome is a genetic disorder which is classified under Pervasive Developmental Disorders in the diagnostic manuals.
- Fragile X Syndrome. The most common chromosonal disorder next to Down’s Syndrome, affecting 1 in 1,200 people.
- Down Syndrome.
- Landau Kleffner Syndrome.
- Angelman Syndrome.
What are the 3 types of Down syndrome?
There are three types of Down syndrome: trisomy 21 (nondisjunction), translocation and mosaicism.
- Trisomy 21, the most common type of Down syndrome, occurs when there are three, rather than two, number 21 chromosomes present in every cell of the body.
- Translocation accounts for 4% of all cases of Down syndrome.
Why is Down syndrome called a syndrome and not a disease?
In the field of medical genetics, the term “syndrome” is traditionally only used when the underlying genetic cause is known. Thus, Trisomy 21 is commonly known as Down syndrome. The consensus underlying cause of VACTERL association has not been determined, and thus it is not commonly referred to as a “syndrome”.
What are some common chromosomal disorders?
Some chromosomal abnormalities occur when there is an extra chromosome, while others occur when a section of a chromosome is deleted or duplicated. Examples of chromosomal abnormalities include Down syndrome, Trisomy 18, Trisomy 13, Klinefelter syndrome, XYY syndrome, Turner syndrome and triple X syndrome.
What disease is caused by one less chromosome?
There are 2 types of Turner syndrome: monosomy X TS and mosaic TS. About half of all girls with Turner syndrome have a monosomy disorder. Monosomy means that a person is missing one chromosome in the pair. Instead of 46 chromosomes, the person has only 45 chromosomes.