22q Deletion Syndrome (22q DS) is a complex condition which
gives rise to nearly 200 different symptoms. It is cited as the commonest
genetic deletion syndrome (Fomin et al, 2010). No one person affected by the condition
will exhibit all of the symptoms, although it is probable that different
symptoms will become evident throughout the individual's life. On
average, individuals could experience around 30 symptoms in their lifetime.
22q DS is now the accepted name for the syndrome,
encompassing all symptoms. Variants of the syndrome are frequently known as
Velo-Cardio Facial Syndrome (VCFS), DiGeorge Syndrome (DGS), Shprintzen's
Syndrome and CATCH-22 depending on the nature of the symptoms presented by the
patient.
22q DS is a spectrum condition. This means that all
individuals will be affected by different collections of symptoms and to
greater or lesser degrees. Although the cause is a variable deletion on
the "q" branch of the 22nd chromosome, there does not currently appear to be any
correlation between the size of the deletion and the severity of its effects.
Some of the common symptoms include:
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A full list of all the symptoms and more information on some of these symptoms
Here is an excellent guide to 22q DS created by Unique, a charity based in south-eastern England. This
guide was updated in 2011 and to review the document for authority, Unique
solicited the assistance of Dr Robert Shprintzen himself!
The incidence of the syndrome isn't fully agreed; a scale of
values is presented around the web. Many estimate a figure of 1:2000, though we
have seen figures as high as 1:900, whilst some more typically older material
estimate incidence at between 1:4000 - 1:8000. As awareness of 22q DS
increases, and more people are tested, we expect greater reliability in the
figure. By comparison, Down's Syndrome has an estimated incidence of 1:733.
Genetic testing is available to confirm diagnosis of 22q DS,
via the fluorescence in-situ hybridisation (FISH) test.
Genetic counselling is often provided when a diagnosis is made, to establish
whether other family members have 22q DS or not.
Most children born with 22q DS - more than 90% - have a
"de novo" deletion; that is they have not inherited the condition
from a parent. De novo deletions occur when parental sperm or an egg is formed with
missing genetic material on chromosome 22 branch 11q. This area of chromosome
22 is prone to rearrangement during sperm or egg formation. Recent studies have
been focused on what appears to be a key missing gene named "TBX1".
A person with 22q DS has a 50% chance of passing the genetic
deletion to their offspring. The diagram
below shows how 22q DS can be passed on through families.
You can read more about 22q DS on Wikipedia: https://en.wikipedia.org/wiki/DiGeorge_syndrome
22q11.2 deletion: the most common syndrome you have never heard of
By Hayley Moulding, Cardiff University, May 16, 2017
What Does 22q11.2 Deletion Syndrome Mean? A visual and simple explanation of the condition in plain English suitable for all ages. I created this document to explain 22q DS to a group of students with special needs.
Glossary:
Chromosome: a
thread-like structure of nucleic acids and protein found in the nucleus of most
living cells, carrying genetic information in the form of genes.
Fluorescence in-situ hybridisation (FISH): a molecular
cytogenetic technique that uses fluorescent probes that bind to only those
parts of the chromosome with a high degree of sequence complementarity. It was
developed by biomedical researchers in the early 1980s and is used to
detect and localize the presence or absence of specific DNA sequences on chromosomes. (extract from en.wikipedia.org; 23 May
2017)
TBX1: a protein that in humans is encoded by
the TBX1 gene. Genes in the T-box family play important roles
in the formation of tissues and organs during embryonic development.
The T-box 1 protein appears to be necessary for
the normal development of large arteries that carry blood out of the heart, muscles and bones of the face and neck, and
glands such as the thymus and parathyroid. (extracts
from en.wikipedia.org; 23 May 2017)
