Phelan-McDermid Syndrome

National Organization for Rare Disorders, Inc.

Skip to the navigation

It is possible that the main title of the report Phelan-McDermid Syndrome is not the name you expected.

Disorder Subdivisions

  • None

General Discussion

Phelan-McDermid syndrome is a rare chromosomal disorder in which a portion of the long arm (q) of chromosome 22 is missing (deleted or monosomic). Although the range and severity of symptoms may vary, Phelan-McDermid syndrome is generally thought to be characterized by low muscle tone, normal to accelerated growth, absent to severely delayed speech, moderate to profound mental retardation, and minor dysmorphic features. A rare number of cases with much smaller (submicroscopic) deletions of 22q13 are reported to result in mild developmental delay. Current research indicates that the inability of the gene involved to produce sufficient protein for normal functioning (haploinsufficiency) may be responsible for most of the neurologic symptoms (developmental delay and absent speech) associated with this disorder.

Supporting Organizations

Chromosome 22 Central

c/o Murney Rinholm
7108 Partinwood Drive
Fuquay-Varina, NC 27526
Tel: (919)567-8167

Chromosome Disorder Outreach, Inc.

P.O. Box 724
Boca Raton, FL 33429-0724
Tel: (561)395-4252
Fax: (561)395-4252

Genetic and Rare Diseases (GARD) Information Center

PO Box 8126
Gaithersburg, MD 20898-8126
Tel: (301)251-4925
Fax: (301)251-4911
Tel: (888)205-2311

Phelan-McDermid Syndrome Foundation

200 Capri Isles Blvd
Suite 7F
Venice, FL 34284
Tel: (941)485-8000
Fax: (941)485-8000

UNIQUE - Rare Chromosome Disorder Support Group

G1 The Stables
Station Road West
Oxted, RH8 9EE
United Kingdom
Tel: 0044 (0)1883 723356

For a Complete Report

This is an abstract of a report from the National Organization for Rare Disorders (NORD). For a full-text version of this report, go to and click on Rare Disease Database under "Rare Disease Information".

The information provided in this report is not intended for diagnostic purposes. It is provided for informational purposes only.

It is possible that the title of this topic is not the name you selected. Please check the Synonyms listing to find the alternate name(s) and Disorder Subdivision(s) covered by this report.

This disease entry is based upon medical information available through the date at the end of the topic. Since NORD's resources are limited, it is not possible to keep every entry in the Rare Disease Database completely current and accurate. Please check with the agencies listed in the Resources section for the most current information about this disorder.

Last Updated:  5/26/2008
Copyright  2005 National Organization for Rare Disorders, Inc.