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Disease Profile

Mosaic trisomy 8

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 8; Trisomy 8 mosaicism


Chromosome Disorders; Congenital and Genetic Diseases


Mosaic trisomy 8 is a chromosomal abnormality that can affect many parts of the body. In individuals with mosaic trisomy 8, some of the body's cells have three copies of chromosome 8 (trisomy), while other cells have the usual two copies of this chromosome. The signs and symptoms vary, but may include distinctive facial features; intellectual disability; and joint, kidney, cardiac, and skeletal abnormalities. Males are more frequently affected than females. In the absence of serious problems, life expectancy is normal, while complete trisomy 8 is lethal and often results in miscarriage during the first trimester. Most cases are not inherited; it often occurs sporadically as a random event during the formation of the reproductive cells (egg and sperm). Diagnosis is based on analysis of chromosomes via genetic testing, such as karyotype. Treatment varies depending on associated symptoms, but typically requires a multidisciplinary team approach.[1][2]


The signs and symptoms of mosaic trisomy 8 vary but may include:

  • Characteristic facial features such as elongation of the skull (scaphocephaly), prominent forehead, widely-spaced eyes, deeply set eyes, broad upturned nose, and micrognathia
  • Brain malformations such as agenesis of the corpus callosum
  • Highly arched or cleft palate
  • Shortened neck with extra skin folds
  • Long slim body with a narrow chest, shoulders, and pelvis
  • Kidney and cardiac abnormalities
  •  Camptodactyly and stiff joints
  • Absent malformed kneecap
  • Vertebral malformations such as scoliosis
  • Eye abnormalities 

Most individuals with mosaic trisomy 8 have moderate intellectual disabilities (IQ between 50 and 75), with some people having a normal intelligence. There is no known connection between the percentage of trisomic cells and the severity of the intellectual disability. Mosaic trisomy 8 also may increase the risk for infections, and seems to increase the risk for certain cancers such as Wilms tumor, myelodysplasia, and acute myeloid leukemia.[1][2]

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
Intellectual disability, moderate
IQ between 34 and 49
30%-79% of people have these symptoms
Abnormality of the antihelix
Abnormality of the ribs
Rib abnormalities
Broad nasal tip
Broad tip of nose
Broad, upturned nose
Increased breadth of nasal tip
Increased breadth of tip of nose
Increased width of nasal tip
Increased width of tip of nose
Nasal tip, broad
Nasal tip, wide
Wide tip of nose

[ more ]

Camptodactyly of finger
Permanent flexion of the finger
Corneal opacity
Deep palmar crease
Deep palm line
Deep plantar creases
Deep wrinkles in soles of feet
Deeply set eye
Deep set eye
Deep-set eyes
Sunken eye

[ more ]

Long, narrow head
Tall and narrow skull

[ more ]

Frontal bossing
Wide-set eyes
Widely spaced eyes

[ more ]

Limitation of joint mobility
Decreased joint mobility
Decreased mobility of joints
Limited joint mobility
Limited joint motion

[ more ]

Long face
Elongation of face
Increased height of face
Increased length of face
Vertical elongation of face
Vertical enlargement of face
Vertical overgrowth of face

[ more ]

Large ears
Little lower jaw
Small jaw
Small lower jaw

[ more ]

Narrow chest
Low chest circumference
Narrow shoulders

[ more ]

Narrow pelvis bone
Patellar aplasia
Absent kneecap
Protruding ear
Prominent ear
Prominent ears

[ more ]

Squint eyes

[ more ]

Vertebral segmentation defect
Vesicoureteral reflux
Wide nose
Broad nose
Increased breadth of nose
Increased nasal breadth
Increased nasal width
Increased width of nose

[ more ]

5%-29% of people have these symptoms
Abnormality of cardiovascular system morphology
Agenesis of corpus callosum
Arthrogryposis multiplex congenita
Cleft palate
Cleft roof of mouth
Clinodactyly of the 5th finger
Permanent curving of the pinkie finger
Undescended testes
Undescended testis

[ more ]

Decreased testicular size
Small testes
Small testis

[ more ]

Hearing impairment
Hearing defect

[ more ]

High palate
Elevated palate
Increased palatal height

[ more ]

Hypopigmented skin patches
Patchy loss of skin color
Short neck
Decreased length of neck
Short stature
Decreased body height
Small stature

[ more ]

Tall stature
Increased body height


Most cases of mosaic trisomy 8 occur due to a random event during the formation of the reproductive cells (egg and sperm) or after fertilization has taken place. An error in cell division (called nondisjunction) may cause some eggs or sperm to have an abnormal number of chromosomes. If an egg or sperm with an extra chromosome 8 contributes to the genetic makeup of an embryo, the embryo will have an extra copy of chromosome 8 in each cell. As the embryo grows and divides, an attempt may be made to correct the mistake by eliminating one extra chromosome 8. In individuals with mosaic trisomy 8, this attempt may be partly successful, leaving some cells with an extra chromosome 8 and some cells with the extra chromosome deleted (the usual chromosome number). This correction process is called trisomy rescue.[2]

In other cases, the egg and sperm may have a normal number of chromosomes, but an error of cell division (nondisjunction) occurs when the fertilized egg is growing and dividing. If an error occurs during one of the divisions, it can cause some cells to have an abnormal number of chromosomes. In people affected by mosaic trisomy 8, some of the body's cells have the usual two copies of chromosome 8, and other cells have three copies of this chromosome (trisomy). The percentage of cells with trisomy 8 and which parts of the body are affected vary from person to person. This leads to variability in the range and severity of symptoms.[2]


Because mosaic trisomy 8 affects many different areas of the body, medical management often involves a team of doctors and other healthcare professionals. Treatment for mosaic trisomy 8 varies depending on the signs and symptoms present in each individual. For example, for individuals with delays in motor skills such as walking, physical therapy or occupational therapy may be helpful. Early intervention and special education may be recommended depending on the degree of intellectual disability. If present, cleft palate, cardiac malformations, and kidney malformations may need to be surgically repaired. Other surgeries and interventions may be needed depending on the nature and severity of the other features and their symptoms.[2]


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

    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

    • Genetics Home Reference (GHR) contains information on Mosaic trisomy 8. 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 8.

      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 8. Click on the link to view a sample search on this topic.

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