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Disease Profile

Mosaic trisomy 14

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.


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 chromosome 14; Trisomy 14 mosaicism


Chromosome Disorders; Congenital and Genetic Diseases


Mosaic trisomy 14 is a rare chromosomal disorder in which there are 3 copies (trisomy) of chromosome 14 in some cells of the body, while other cells have the usual two copies. The extent and severity of features in affected individuals can vary. Signs and symptoms that have been most commonly reported include intrauterine growth restriction; failure to to thrive; developmental delay; intellectual disability; distinctive facial characteristics; structural malformations of the heart; and other physical abnormalities.[1][2] This condition is most often caused by an error in cell division in the egg or sperm cell before conception, or in fetal cells after fertilization. Treatment is directed toward the specific signs and symptoms in each individual.[1]


The effects of mosaic trisomy 14 can vary considerably among affected individuals. Some children with mosaic trisomy 14 grow into healthy, if small, children. Others may have continued difficulty thriving.[2] Those that have a low percentage of affected cells may have fewer and/or less severe symptoms than those with a high percentage of affected cells.[1] Some of the more commonly reported characteristics of the condition include:[1][2]

  • intrauterine growth restriction
  • feeding difficulties
  • failure to thrive
  • some degree of developmental delay or intellectual disability
  • slightly asymmetrical growth
  • abnormal skin pigmentation
  • structural defect(s) of the heart such as tetralogy of Fallot
  • minor genital abnormalities in boys such as undescended testes
  • distinctive facial characteristics such as a prominent forehead; widely spaced eyes; a broad nasal bridge; low-set, malformed ears; a small lower jaw; a large mouth and thick lips; eye abnormalities; or abnormality of the roof of the mouth (palate)

Skeletal abnormalities have also been reported and include dislocation of the hips; overlapping of certain fingers or toes; and/or other features.[1]

This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.

Medical Terms Other Names
Learn More:
80%-99% of people have these symptoms
Abnormality of cardiovascular system morphology
Abnormality of chromosome segregation
Failure to thrive
Faltering weight
Weight faltering

[ more ]

Frontal bossing
Global developmental delay
High palate
Elevated palate
Increased palatal height

[ more ]

Intellectual disability
Mental deficiency
Mental retardation
Mental retardation, nonspecific

[ more ]

Little lower jaw
Small jaw
Small lower jaw

[ more ]

Prominent nasal bridge
Elevated nasal bridge
High nasal bridge
Prominent bridge of nose
Prominent nasal root
Protruding bridge of nose
Protruding nasal bridge

[ more ]

Short neck
Decreased length of neck
Wide mouth
Broad mouth
Large mouth

[ more ]

Wide nasal bridge
Broad nasal bridge
Broad nasal root
Broadened nasal bridge
Increased breadth of bridge of nose
Increased breadth of nasal bridge
Increased width of bridge of nose
Increased width of nasal bridge
Nasal bridge broad
Wide bridge of nose
Widened nasal bridge

[ more ]

30%-79% of people have these symptoms
Anteverted nares
Nasal tip, upturned
Upturned nasal tip
Upturned nose
Upturned nostrils

[ more ]

Bilateral single transverse palmar creases
Narrow opening between the eyelids
Cleft palate
Cleft roof of mouth
Undescended testes
Undescended testis

[ more ]

Ectopic anus
Abnormal anus position
Wide-set eyes
Widely spaced eyes

[ more ]

Hypoplasia of penis
Underdeveloped penis
Low-set, posteriorly rotated ears
Small ears
Underdeveloped ears

[ more ]

Narrow chest
Low chest circumference
Narrow shoulders

[ more ]

5%-29% of people have these symptoms
Abnormality of the ribs
Rib abnormalities
Aplasia/Hypoplasia affecting the eye
Absent/small eye
Absent/underdeveloped eye

[ more ]

Camptodactyly of finger
Permanent flexion of the finger
Lower limb asymmetry
Left and right leg differ in length or width
Drooping upper eyelid


Individuals with mosaic trisomy 14 have a duplication of chromosome 14 material in some of their cells, while other cells have a normal chromosomal makeup. The additional chromosomal material is responsible for the features that are characteristic of the condition.[1]

Most cases of mosaic trisomy 14 appear to result from random errors in the separation of chromosomes (nondisjunction) -either during the division of the egg or sperm in one of the parents, or during cell division after fertilization. There have been some reports in which it may have occurred due to other phenomenon, such as uniparental disomy or the formation of an isochromosome. Uniparental disomy is when an affected individual inherits both copies of a chromosomal pair from one parent, rather than one copy from each parent. An isochromosome is an abnormal chromosome with identical arms on each side of the centromere.[1]

Unique has a leaflet on their Web site that contains additional descriptions and illustrations of how mosaic trisomy 14 may occur. Click here to view the leaflet.


Treatment for signs and symptoms of mosaic trisomy 14 focuses on the specific features present in each individual. Infants with congenital heart defects may need surgery or other therapies to alleviate symptoms and correct heart malformations. Respiratory infections should be treated aggressively and early. Some infants and children with the condition may need surgical repair of certain craniofacial, genital, or other abnormalities. Early intervention may be important in ensuring that children with the reach their potential. Special services that may be beneficial include special education, physical therapy, and/or other medical, social, and/or vocational services.[1]


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

    Social Networking Websites

      Learn more

      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.

      Where to Start

      • 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.

        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. Click on the link.

      • Genetics Home Reference (GHR) contains information on Mosaic trisomy 14. This website is maintained by the National Library of Medicine.
      • Unique is a source of information and support to families and individuals affected by rare chromosome disorders. Click on the link to view information about mosaic trisomy 14.
      • The National Organization for Rare Disorders (NORD) has a report for patients and families about this condition. NORD is a patient advocacy organization for individuals with rare diseases and the organizations that serve them.

        In-Depth Information

        • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
        • 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 Mosaic trisomy 14. Click on the link to view a sample search on this topic.


          1. Chromosome 14, Trisomy Mosaic. NORD. May 26, 2008; https://www.rarediseases.org/rare-disease-information/rare-diseases/byID/999/viewAbstract. Accessed 11/13/2012.
          2. Trisomy 14 mosaicism. Unique. 2008; https://www.rarechromo.org/information/Chromosome%2014/Trisomy%2014%20mosaicism%20FTNW.pdf. Accessed 11/14/2012.

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