National Center for Advancing and Translational Sciences Genetic and Rare Diseases Information Center, a program of the National Center for Advancing and Translational Sciences

Trisomy 2 mosaicism


Other Names:
Mosaic trisomy 2
Categories:
Trisomy 2 mosaicism is a rare chromosome disorder characterized by having an extra copy of chromosome 2 in a proportion, but not all, of a person’s cells. Many cases of trisomy 2 mosaicism result in miscarriage during pregnancy. In infants born with trisomy 2 mosaicism, severity as well as signs and symptoms vary widely. Features of trisomy 2 mosaicism may include intrauterine growth restriction (IUGR), any of various birth defects, distinctive facial features, growth delay, developmental delays, and intellectual disabilities.[1][2] However, children with trisomy 2 mosaicism with no significant medical problems have been reported (although long-term follow-up was not available).[2] The severity and specific symptoms present generally 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.[3][4]
Last updated: 6/1/2018
The severity and specific symptoms associated with trisomy 2 mosaicism can vary considerably and generally depend on the level of mosaicism (proportion of affected cells) and the location and type of cells affected. Children with no significant medical problems have been reported, as well as children with major birth defects and serious health issues.[2]

During pregnancy (prenatally), trisomy 2 mosaicism may be associated with various findings, such as:

Signs and symptoms that have been reported in livebirths with trisomy 2 mosaicism include:

  • distinctive head and facial features such as a flattened appearance of the middle part of the face (midface hypoplasia), absence of one or both eyes (anophthalmia) or abnormally small eyes (microphthalmia), cleft lip and palate, wide-set eyes (hypertelorism), and small head size (microcephaly)
  • growth and motor delay
  • intellectual disability
  • congenital heart defects
  • neural tube defects
  • diaphragmatic hernia
  • inguinal hernia
  • radioulnar hypoplasia
  • rocker-bottom feet (feet with a rounded bottom, resembling the bottom of a rocking chair)
  • abnormal development of the lower end of the spine (caudal dysgenesis)
  • portal fibrosis
  • intestinal malrotation (twisting of the intestines)
  • Hirschsprung disease
  • hypomelanosis of Ito
  • polydactyly
  • deafness
  • undescended testes
  • face and body asymmetry
  • clubfoot
  • lack of sacrum[4][5]
Because few cases have been reported in the literature and the level of mosaicism differs among affected fetuses and individuals, it is not possible to predict how a pregnancy or person may be affected by trisomy 2 mosaicism.
Last updated: 6/1/2018
The long-term outlook (prognosis) associated with trisomy 2 mosaicism is difficult to predict and depends on many factors. These factors may include the level of mosaicism (proportion of cells affected); the location and type of the cells affected (which cannot be predicted); the nature of abnormal ultrasound findings (if detected); and potential pregnancy-related or health-related complications that may arise before or after birth. A range of outcomes have been reported, including miscarriage, stillbirth, pregnancy termination after abnormal ultrasound findings or prenatal diagnosis, favorable pregnancy outcome, apparently healthy newborn, and any of many mild to severe birth defects.[4][6] Few cases of trisomy 2 mosaicism have been reported in livebirths.[5]

When trisomy 2 mosaicism is diagnosed (in a fetus or child), it can be difficult to estimate the true level of mosaicism because levels can differ depending on the nature of the sample tested. Different levels of mosaicism may be found in the same pregnancy using various lab techniques in samples obtained by chorionic villus sampling, amniocentesis (both uncultured and cultured cells), and cord blood sampling.[6] Likewise, different levels of mosaicism may be found in a liveborn when samples are obtained for urinary analysis, blood analysis, or tissue analysis. For example, a blood test can only determine the level of mosaicism in the blood cells.

During pregnancy, because it is not possible to predict the outcome for all fetuses diagnosed with trisomy 2 mosaicism, health care professionals may recommend a variety of additional tests to obtain as much information as possible about how a fetus is developing. Tests that may be recommended may include analysis of other types of prenatal samples, more detailed ultrasound exams, fetal echocardiography to evaluate the fetal heart, and/or fetal MRI. Prognosis information in each individual case may be based on results of these tests and the outlook associated with specific findings.
Last updated: 6/2/2016

Research helps us better understand diseases and can lead to advances in diagnosis and treatment. This section provides resources to help you learn about medical research and ways to get involved.

Patient Registry

  • The Tracking Rare Incidence Syndromes (TRIS) project seeks to increase the knowledge base on rare incidence trisomy conditions, and to make this information available to families and interested educational, medical and therapeutic professionals.

    TRIS Project
    Deborah A. Bruns, Ph.D., Principal Investigator
    Counseling, Quantitative Methods, and Special Education
    Wham Building, Room 223 MC 4618
    Carbondale, IL 62901
    Phone: 618-453-2311
    E-mail: tris@siu.edu

Support and advocacy groups can help you connect with other patients and families, and they can provide valuable services. Many develop patient-centered information and are the driving force behind research for better treatments and possible cures. They can direct you to research, resources, and services. Many organizations also have experts who serve as medical advisors or provide lists of doctors/clinics. Visit the group’s website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD.

Organizations Supporting this Disease

These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

In-Depth Information

  • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.
  • PubMed is a searchable database of medical literature and lists journal articles that discuss Trisomy 2 mosaicism. Click on the link to view a sample search on this topic.

Selected Full-Text Journal Articles

Questions sent to GARD may be posted here if the information could be helpful to others. We remove all identifying information when posting a question to protect your privacy. If you do not want your question posted, please let us know. Submit a new question

  • During pregnancy, amniocentesis detected mosaic trisomy 2, and several abnormal ultrasound findings were detected. Can you give a prediction for survival and prognosis, including mental capacity? See answer


  1. Gupta S et al. Trisomy 2 mosaicism in hypomelanosis of Ito. Am J Med Genet Part A. 2007;
  2. Chen CP, Su YN, Chern SR, et al. Mosaic trisomy 2 at amniocentesis: prenatal diagnosis and molecular genetic analysis. Send to Taiwan J Obstet Gynecol. December, 2012; 51(4):603-611. https://www.ncbi.nlm.nih.gov/pubmed/23276565.
  3. McKinlay Gardner RJ, Southerland GR. Chromosome Abnormalities and Genetic Counseling. New York, NY: Oxford University Press, Inc; 2004;
  4. 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.
  5. Paolo Prontera, Gabriela Stangoni, Carmela Ardisia, Daniela Rogaia, Amedea Mencarelli and Emilio Donti. Trisomy 2 mosaicism with caudal dysgenesis, Hirschsprung disease, and micro-anophthalmia. American Journal of Medical Genetics Part A. April, 2011; 155(4):928-930.
  6. Chih-Ping Chen, et. al. Prenatal diagnosis of low-level mosaicism for trisomy 2 associated with a favorable pregnancy outcome. Taiwanese Journal of Obstetrics and Gynecology. April, 2016; 55(2):303-304.
  7. Sifakis S, Staboulidou I, Maiz N, Velissariou V, Nicolaides KH. Outcome of pregnancies with trisomy 2 cells in chorionic villi.. Prenat Diagn. 2010 Apr;