22q13 Deletion Syndrome or Phelan-McDermid Syndrome July 2006

A condition represented by multiple names is not an unusual occurrence in genetics. For example, a very common condition Down syndrome is also called Trisomy-21. The genetic condition in this article is also known by two names; the first name is descriptive of the structural abnormality found in the chromosome and the other name recognizes two key individuals involved in the research and identification of the syndrome.

22q13 Deletion Syndrome or Phelan-McDermid Syndrome is a rare chromosomal disorder in which a portion of the long arm or q arm of chromosome 22 is missing. The following diagram represents chromosome 22, one of the 23 pairs of chromosomes in humans:

A significant concern when a section of a chromosome is absent is that key functioning genes may be affected or missing as well and that is true of Phelan-McDermid Syndrome. It is believed that absence or abnormal functioning of a particular gene is the primary cause for the characteristics of this syndrome. This gene is a key player in the development of the central nervous system and its loss prevents normal brain development.

There is a wide range and severity of symptoms but most patients will have low or floppy muscle tone, absent or severely delayed speech, normal or accelerated growth, and developmental delays.

There are more than 270 diagnosed cases worldwide; reliable chromosome testing became available only in 1998 so it is suspected that there are many more undiagnosed individuals.

Beginning in 1998 and every two years following, families from around the world are invited to attend the Phelan-McDermid Support Group Conference to interact with other families, to learn about current research, possible treatments, and coping strategies for a child with special needs. The July 2006 Conference will be in Greenville, South Carolina and is organized and managed by the Greenville office of the Greenwood Genetic Center. Currently there are 103 families registered to attend; a significant increase from the 60 families that attended in 2004. The Conference is an invaluable means of support and communication for these children and their families.

Note: M.C. Phelan, Ph.D. was associated with the Greenwood Genetic Center from 1982-2000.