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Disease Profile

Trisomy 2 mosaicism

Prevalence estimates on Rare Medical Network websites are calculated based on data available from numerous sources, including US and European government statistics, the NIH, Orphanet, and published epidemiologic studies. Rare disease population data is recognized to be highly variable, and based on a wide variety of source data and methodologies, so the prevalence data on this site should be assumed to be estimated and cannot be considered to be absolutely correct.

<1 / 1 000 000

US Estimated

Europe Estimated

Age of onset





Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease.


Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype.


dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.


recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder.


Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.


Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.


Not applicable


Other names (AKA)

Mosaic trisomy 2


Chromosome Disorders; Congenital and Genetic Diseases


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]


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.


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

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    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


        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;

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