Wikipedia defines 22q13 deletion syndrome this way:
“…a genetic disorder caused by deletions or rearrangements on the q terminal end (long arm) of chromosome 22. Any abnormal genetic variation in the q13 region that presents with significant manifestations (phenotype) should be diagnosed as [22q13 deletion syndrome].” It goes on to say “There are over 250 known genes and gene regulator sites in the 22q13 region.”
22q13 deletion syndrome is sometimes called Phelan-McDermid syndrome (PMS). 22q13 deletion syndrome was first observed as a terminal deletion of chromosome 22 (Nesslinger et al., 1994). Other major deletions in that region are still considered 22q13 deletion syndrome. The term PMS was introduced by The Phelan-McDermid Syndrome Foundation, which adopted that name for the Foundation. An attempt to build a scientific consensus on the definition of PMS in 2012 ended in disarray.
Different scientists and clinicians now use the term PMS differently. Some use PMS to describe any intellectual disability or autism caused by deletion or mutation of SHANK3, excluding cases of interstitial deletion or mutations of other genes. For example, “…deletions and mutations that lead to a loss of a functional copy of SHANK3 cause Phelan-McDermid syndrome” (Betancur and Buxbaum, 2013). This follows the “SHANK3 hypothesis of PMS”, which is widely cited, but unproven. Other experts in the field define PMS as deletion or mutation of any gene(s) in the 22q13 region, as long as the individual presents with manifestations typical of 22q13 deletion syndrome: “Almost all of these deletions include the gene SHANK3…” (Phelan and McDermid, 2012). At the present writing, the Foundation web site (http://22q13.org) avoids a detailed operational definition. Rather, it describes “typical causes” and focuses discussion on SHANK3, somewhat echoing the SHANK3 hypothesis of PMS.
My son, David has 22q13 deletion syndrome, but he also has an overdose (trisomy) of chromosome 19. Is that PMS? Who knows? Most people say “yes,” but it is hard to diagnose what has not been clearly defined. Recently, I was asked by a mother to make sense of a genetic report from a prestigious university-affiliated hospital. The report had errors owing to the confusion between what constitutes PMS and the phenotype characteristics of 22q13 deletion syndrome. Because of those errors, the recommendations were flawed. One goal of my blog will be to inform parents, scientists and clinicians in the hope of reducing errors and separating facts from conjecture.
As with the definition of PMS, much of science can be messy. Most discussions of science oversimplify the realities. This blog is dedicated to those parents, clinicians and researchers who try to make sense of genetic defects that can arise from the q13 region of chromosome 22, whatever you call it. It is aimed at parents who live with it and deal with it every day. It is for anyone who wants to understand more. All sources of information are biased and perhaps my bias suits you, or at minimum, is informative.
There are only about 1,100 identified cases of 22q13 deletion syndrome world-wide. That leaves little opportunity to find a parent who has raised a child and is also a scientific expert in the field. If there were such a parent, s/he would be almost obligated to start a blog. So, that is what I have done.
If you have not clicked on “Who is arm22q13” on the front page of my blog, be sure you do that soon.
I hope you are not too disappointed with this first post. The real point is to keep myself out of trouble. It is a disclaimer. Please read it and keep it in mind as you read my subsequent, far more interesting, posts.
This blog will be full of statements: scientific, personal, experiential, opinionated, political and maybe even hostile. All of the statements are mine, alone. None of these statements are to be taken as a reflection of my employer or any other organization. I make no pretense of representing any organization or employer. Any errors, misstatements, wrong facts, wrong attributions or other misdeeds are my responsibility. One of my employers is an agency of a government I do not represent or speak for the agency or the government either on or off the record. This blog is a personal undertaking for the benefit of my fellow parents who must deal with the often painful reality of raising a child with 22q13 deletion syndrome.