Chromosome 9, Trisomy 9p (Multiple Variants)

National Organization for Rare Disorders, Inc.

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It is possible that the main title of the report Chromosome 9, Trisomy 9p (Multiple Variants) is not the name you expected. Please check the synonyms listing to find the alternate name(s) and disorder subdivision(s) covered by this report.


  • Chromosome 9, Complete Trisomy 9P
  • Chromosome 9, Partial Trisomy 9P, Included
  • Chromosome 9, Trisomy 9pter-q11-13, Included
  • Chromosome 9, Trisomy 9pter-q22-32, Included
  • Dup(9p) Syndrome
  • Duplication 9p Syndrome
  • Rethore Syndrome (obsolete)
  • Trisomy 9P Syndrome (Partial), Included

Disorder Subdivisions

  • None

General Discussion

Chromosome 9, trisomy 9p is a rare chromosomal syndrome in which a portion of the 9th chromosome appears three times (trisomy) rather than twice in cells of the body. Chromosomes are found in the nucleus of all body cells. They carry the genetic characteristics of each individual. Pairs of human chromosomes are numbered from 1 through 22, with an unequal 23rd pair of X and Y chromosomes for males and two X chromosomes for females. Each chromosome has a short arm designated as "p," a long arm identified by the letter "q," and a narrowed region at which the two arms are joined (centromere). Chromosomes are further subdivided into bands that are numbered outward from the centromere. For example, the short arm of chromosome 9 includes bands 9p11 to 9p24, and the long arm includes bands 9q11 to 9q34.
In trisomy 9p, the trisomy (or duplicated material) may involve a portion of the short arm (9p), the entire short arm, or the short arm and a portion of the long arm (9q) of chromosome 9. Evidence suggests that, in many cases, associated symptoms and findings may be relatively similar among affected infants despite differing lengths of the trisomic (duplicated) segment of 9p. However, in those with larger trisomies (e.g., extending to middle or end [distal] regions of 9q), additional features may also be present that appear to correlate with the extent of the duplication. Additionally, certain individuals with duplications of specific areas of chromosome 9p have developed any symptoms or only very mild or subtle symptoms.
Children with Trisomy 9p are affected by delays in reaching developmental milestones like crawling or walking (developmental delays), growth deficiency, and distinctive malformations of the skull and facial (craniofacial) region. As children grow older, intellectual disability may become apparent.
In some instances, additional physical abnormalities may also be present, such as other skeletal defects and/or structural malformations of the heart that are present at birth (congenital heart defects). In some cases, the trisomy appears to result from a balanced chromosomal rearrangement in one of the parents; in others, it is thought to arise from spontaneous (de novo) errors very early in embryonic development that occur for unknown reasons (sporadically).
The chromosomal abnormality was originally reported in the medical literature in1970. Trisomy 9p was first proposed as a distinct syndrome with characteristic symptoms and findings in 1975.

Supporting Organizations


PO Box 751112
Las Vegas, NV 89136
Tel: (702)769-9264
Fax: (702)341-5351
Tel: (888)486-1209

American Heart Association

7272 Greenville Avenue
Dallas, TX 75231
Tel: (214)784-7212
Fax: (214)784-1307
Tel: (800)242-8721

Birth Defect Research for Children, Inc.

976 Lake Baldwin Lane
Orlando, FL 32814
Tel: (407)895-0802

Craniofacial Foundation of America

975 East Third Street
Chattanooga, TN 37403
Tel: (423)778-9176
Fax: (423)778-8172
Tel: (800)418-3223

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

March of Dimes Birth Defects Foundation

1275 Mamaroneck Avenue
White Plains, NY 10605
Tel: (914)997-4488
Fax: (914)997-4763

Support Organisation for Trisomy and Related Disorders


Support Organization for Trisomy 13/18 and Related Disorders, UK

c/o Christine Rose
48 Froggatts Ride
West Midlands, B76 2TQ SOFT
United Kingdom
Tel: 1213513122

Support Organization for Trisomy 18, 13, and Related Disorders

2982 S. Union Street
Rochester, NY 14624-1926
Fax: (585)594-1957
Tel: (800)716-7638

The Arc

1825 K Street NW, Suite 1200
Washington, DC 20006
Tel: (202)534-3700
Fax: (202)534-3731
Tel: (800)433-5255

Trisomy 9 International Parent Support (9TIPS)

4027 E. Piedmont Drive
Highland, CA 92346
Tel: (909)862-4470

UNIQUE - Rare Chromosome Disorder Support Group

The Rare Chromosome Disorder Support Group
Surrey, RH8 9EE
United Kingdom
Tel: 441883723356
Email: or

For a Complete Report

This is an abstract of a report from the National Organization for Rare Disorders (NORD). A copy of the complete report can be downloaded free from the NORD website for registered users. The complete report contains additional information including symptoms, causes, affected population, related disorders, standard and investigational therapies (if available), and references from medical literature. For a full-text version of this topic, 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. NORD recommends that affected individuals seek the advice or counsel of their own personal physicians.

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.

For additional information and assistance about rare disorders, please contact the National Organization for Rare Disorders at P.O. Box 1968, Danbury, CT 06813-1968; phone (203) 744-0100; web site or email

Last Updated:  12/31/1969
Copyright  2015 National Organization for Rare Disorders, Inc.