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Genetic and Rare Diseases Information Center (GARD)

Trisomy 2 mosaicism

Other Names for this Disease
  • Mosaic trisomy 2
See Disclaimer regarding information on this site. Some links on this page may take you to organizations outside of the National Institutes of Health.

Your Question

Our daughter was recently diagnosed with mosaic trisomy 2.  Since birth she has always had an undiagnosed syndrome.  We felt relieved that we finally knew what she was born with but we have not been able to find any information about it. What can you provide us?

Our Answer

We have identified the following information that we hope you find helpful. If you still have questions, please contact us.

Below we have provided information on chromsome abnormalities in general, followed by information specific to trisomy 2 mosaicism. 

Note:  This information is meant for individuals with trisomy 2 mosaicism and their families. Trisomy 2 mosaicism may also be encountered during pregnancy as a finding following chorionic villus sampling. In these situations the trisomic cells are most often confined to the placenta and the pregnancy results in a healthy infant. Further investigation is warranted however, because in a small percentage of cases this finding can be associated increased pregnancy risks. Questions regarding trisomy 2 mosaicism should be discussed with a genetic professional. Click here to visit GeneTests to search for a genetics professional near you.
Last updated: 4/16/2010

What are chromosomes?

Chromosomes are the structures that hold our DNA. Our DNA contains the instructions, called genes, that tells our bodies how to develop and function. In each human cell, except the egg and sperm cells, there are 46 chromosomes. Our chromosomes come in pairs. One of each pair is inherited from the mother and the other from the father. Each chromosome has a constriction point called the centromere, which divides the chromosome into two sections, or “arms.” The short arm of the chromosome is labeled the “p arm.” The long arm of the chromosome is labeled the “q arm.” Click here to view an illustration of a chromosome and DNA.

More information on chromosomes is available from Genetics Home Reference.
Last updated: 4/16/2010

What is a karyotype?

When the chromosomes are stained and organized into a picture, it is called a karyotype. Staining the chromosomes reveal unique banding patterns that help us identify and label individual regions or parts of the chromosome. Click here to see an illustration of a karyotype.

Today additional chromosome test are available, such as FISH (fluorescence in situ hybridization) and comparative genomic hybridization arrays. Click on the links above to learn more about these genetic tests.
Last updated: 4/16/2010

What is a chromosome anomaly?

A chromosomal anomaly occurs when an individual is affected by a change in the number, size, or structure of his or her chromosomes. The change in the amount or arrangement of the genetic information in the cells may result in problems in growth, development, and/or functioning of the body systems.

You can find additional information on chromosome anomalies in general at the following Web sites.

The National Human Genome Research Institute, part of the National Institutes of Health (NIH), has developed a fact sheet on chromosome abnormalities, which may be helpful to you. To read this information, visit the link below.

MEDLINEplus, the National Library of Medicine Web site designed to direct you to information and resources that help you research your health questions, provides further information about chromosomes at the following link:

Last updated: 6/8/2012

What is a chromosome trisomy? What is mosaicism?

A chromosome trisomy occurs when an extra copy of a chromosome is present in the body's cells. A trisomy can involve any chromosome. How a chromosome trisomy impacts growth and development depends on which chromosome is involved and if the extra chromosome exists in every cell or only in a subset of cells. 

When a trisomy affects only a subset of cells, this is called 'mosaicism.' In mosaic trisomies the percentage of affected body cells and location of affected cells vary from person to person. Because of this it is difficult to compare people with the same mosaic trisomy as they tend to be be very differently affected.

More information on chromosome mosaicism can be found by visiting the Centre for Genetics Education Web page on this topic at the following link:
Last updated: 4/16/2010

What is trisomy 2 mosaicism? 

Trisomy 2 mosaicism is a rare chromosome disorder characterized by having an extra copy of chromosome 2 (three copies in total) in a proportion of a person’s cells. Many cases of trisomy 2 mosaicism result in miscarriage during pregnancy. In infants born with trisomy 2 mosaicism, signs and symptoms vary widely and may include any of various birth defects.[1] The severity and specific symptoms present depend on the level of mosaicism (the proportion of cells affected) and the location or type of affected cells in the body. Trisomy 2 mosaicism is not inherited. It is caused by a random error in cell division during early development of the embryo.

When trisomy 2 mosaicism is detected during early pregnancy with chorionic villus sampling (CVS), the affected cells may be confined only to the placenta, and not present in the fetus. Amniocentesis is typically recommended to confirm this, and monitoring is still warranted due to an increased risk for intrauterine growth restriction, low amniotic fluid level (oligohydramnios), or other complications including stillbirth.[2][3]
Last updated: 6/1/2016

Have cases of live born infants with trisomy 2 mosaicism been reported in the medical literature?

Yes. To date there have been 7 cases of live born infants with trisomy 2 mosaicism reported in the medical literature. The case reports demonstrate great variability in the signs and symptoms associated with trisomy 2 mosaicism. Signs and symptoms reported in these individual cases collectively include:[1][4][5][6]

Intrauterine growth retardation 
Underdevelopment of the corpus callosum
Heart defects
Intellectual impairment
Developmental delay
Neural tube defects
Minor differences in facial appearance (e.g., downturned corners of the mouth, epicanthal folds, wide spaced eyes)
Diaphragmatic hernia
Duodenal atresia
Intestinal malrotation 
Atrial and ventricular septal defect
Short hands and feet with prominent palmar pads
Hypopigmented patches of skin
Cleft lip
Cleft palate
Wide placed nipples
Radio-ulnar hypoplasia
Feet with a rounded bottom (rocker bottom feet)
Bronchopulmonary dysplasia

Last updated: 4/16/2010

How can I learn about the features and outcomes that have been associated with specific cases of trisomy 2 mosaicism?

We recommend that you contact Unique, which collects and provides information about rare chromosome disorders, and links families whose children have similar chromosome disorders. Unique does have several registered genotypes for trisomy 2 mosaicism, which can be viewed here. You can request a description of the symptoms associated with these results by contacting Unique.

Additionally, you can find relevant articles on trisomy 2 mosaicism through PubMed, a searchable database of biomedical journal articles. Although not all of the articles are available for free online, most articles listed in PubMed have a summary available. To obtain the full article, contact a medical/university library or your local library for interlibrary loan. You can also order articles online through the publisher’s Web site. Using "trisomy 2 mosaicism" or "mosaic trisomy 2" as your search term should help you locate articles. View our sample PubMed search for this condition here.

The National Library of Medicine (NLM) Web site has a page for locating libraries in your area that can provide direct access to these journals (print or online). The Web page also describes how you can get these articles through interlibrary loan and Loansome Doc (an NLM document-ordering service). You can access this page at the following link: You can also contact the NLM toll-free at 888-346-3656 to locate libraries in your area.
Last updated: 6/2/2016

How can I learn about research involving trisomy 2 mosaicism?

The Chromosome Deletion Outreach lists a number of ongoing chromosome research studies. You can read more about these studies at the following link to the CDO Web page.  

The National Human Genome Research Institute (NHGRI) has completed an evaluation of patients with unresolved chromosome abnormalities. Further information about this study can be accessed through, a database developed by the U.S. National Institutes of Health, through the National Library of Medicine to provide patients, family members, and members of the public with current information on clinical research studies. To read about this study, visit the hyperlink below. After you click on the study, review its information to determine if it provides you with useful information. Use the study’s contact information to learn more.

To locate information resulting from the completed study entitled, 'Evaluation of Patients with Unresolved Chromosome Abnormalities' (study ID numbers 970045, 97-HG-0045; NLM Identifier NCT00001639), you can either e-mail or call the National Library of Medicine (NLM) Customer Service.  Include the title of the study, the study ID number, and the NLM Identifier, and a librarian at NLM can assist you in searching the medical literature for published results on the completed clinical trial.  

National Library of Medicine Customer Service
Toll-free:  888-346-3656

Oftentimes parents ask us how they can find a researcher who is interested in studing their child's rare chromosome anomaly. We recognize that it can be a challenge to find a researcher who is available and has the funds needed to research a specific condition. Still, we have identified the following resources which may be helpful.

The Genetic Alliance, an international coalition composed of more than 750 advocacy organizations, has created online tools that discuss how to get researchers interested in a disease. To review the information, visit the following link and scroll down to the research section:

ResearchMatch is a free national research registry designed to bring together patients, healthy volunteers and researchers. Anyone from the United States can register with ResearchMatch, and a parent, legal guardian, or caretaker may register on behalf of a volunteer. Researchers from participating institutions use the ResearchMatch database to search for patients or healthy volunteers who meet the study criteria. Many studies are looking for healthy people of all ages, while some are looking for people with specific illnesses. ResearchMatch was developed by major academic institutions across the country and is funded by the National Center for Research Resources (NCRR), a center of the National Institutes of Health (NIH), the primary Federal agency for conducting and supporting medical research.

Last updated: 4/16/2010

  • Gupta S et al. Trisomy 2 mosaicism in hypomelanosis of Ito. Am J Med Genet Part A. 2007;
  • McKinlay Gardner RJ, Southerland GR. Chromosome Abnormalities and Genetic Counseling. New York, NY: Oxford University Press, Inc; 2004;
  • Chen CP, et. al. Prenatal diagnosis of mosaic trisomy 2 associated with abnormal maternal serum screening, oligohydramnios, intrauterine growth restriction, ventricular septal defect, preaxial polydactyly, and facial dysmorphism. Taiwan J Obstet Gynecol. September, 2013; 52(3):395-400.
  • Schinzel A., . Catalogue of Unbalanced Chromosome Aberrations in Man, 2nd ed. Walter de Gruyter GmbH & Co; 2001;
  • Mihci E et al.,. Clinical Dysmorphology. The phenotypic spectrum of trisomy 2: Report of two new cases. 2009;
  • Seller MJ et al.,. A trisomy 2 fetus with severe neural tube defects and other abnormalities. Clinical dysmorphology. 2004;
  • Sifakis S, Staboulidou I, Maiz N, Velissariou V, Nicolaides KH. Outcome of pregnancies with trisomy 2 cells in chorionic villi.. Prenat Diagn. 2010 Apr;
Other Names for this Disease
  • Mosaic trisomy 2
See Disclaimer regarding information on this site. Some links on this page may take you to organizations outside of the National Institutes of Health.