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Disease Profile

Diploid-triploid 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.


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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)

Diploid/triploid mosaicism; Diploid/triploid mixoploidy; Mosaic triploidy


Chromosome Disorders; Congenital and Genetic Diseases


Diploid-triploid mosaicism (DSM) is a genetic condition caused by an abnormal number of chromosomes. Symptoms of this condition may include decreased muscle tone (hypotonia), slow growth, characteristic facial features, fusion or webbing between the fingers and/or toes (syndactyly), and unusual skin pigmentation. Intellectual disabilities may be present. DSM occurs when a person has some cells with three copies of each chromosome for a total of 69 chromosomes (triploid cells) and some cells with the usual 2 copies of each chromosome for a total of 46 chromosomes (diploid cells). Having two or more different cell types is called mosaicism. Diagnosis is made through a clinical exam and a skin biopsy. Treatment is focused on managing the symptoms.


The following list includes the most common signs and symptoms in people with diploid-triploid mosaicism. These features may be different from person to person. Some people may have more symptoms than others and symptoms can range from mild to severe. This list does not include every symptom or feature that has been described in this condition.

Signs and symptoms may include:[1][2]

  • Growth delay
  • Decreased muscle tone (hypotonia)
  • Characteristic facial features
  • Uneven facial and/or body growth
  • Fusion of the fingers or toes (syndactyly)
  • Intellectual disability
  • Developmental delay

Signs and symptoms of diploid-triploid mosaicism are present at birth. Developmental and intellectual disability may also be present. Some people have feeding problems, unusual skin pigment, and fat around the stomach. Because few people have been reported with diploid-triploid mosaicism, little is known about how it changes throughout someone's life.[3]


Diploid-triploid mosaicism (DSM) occurs when a person has two different types of cells with different numbers of chromosomes. In DSM, some cells contain 46 total chromosomes (the usual number) and some cells contain 69 chromosomes (an entire extra set). Mosaicism occurs very early in embryonic development. The severity of this condition is determined by the percent of cells that have 69 chromosomes.[4]


Diploid-triploid mosaicism is diagnosed through a clinical exam, the symptoms, and testing to examine the chromosomes from different types of cells. Testing generally includes a skin biopsy or the investigation of urinary cells.[1][2]


Treatment for diploid-triploid mosaicism is based on managing the symptoms.

Specialists involved in the care of someone with diploid-triploid mosaicism include:

  • Medical geneticist
  • Neurologist
  • Gastroenterologist
  • Developmental specialist


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.

    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.
    • PubMed is a searchable database of medical literature and lists journal articles that discuss Diploid-triploid mosaicism. Click on the link to view a sample search on this topic.


      1. Rittinger, O; Kronberger, G; Pfeifenberger, A; Kotzot, D; Fauth, C. The changing phenotype in diploid triploid mosaicism may mimic genetic syndrome with aberrant genomic imprinting: Follow up in a 14 year old girl. European Journal of Medical Genetics. July 26, 2008; https://www.ncbi.nlm.nih.gov/pubmed/18706534.
      2. Boonen SE, Hoffmann AL, Donnai D, Tümer Z, Ravn K. Diploid/triploid mosaicism: a rare event or an under-diagnosed syndrome?. Eur J Med Genet. 2011; 54(3):374-375. https://pubmed.ncbi.nlm.nih.gov/21252005.
      3. Lalani FK, Elsner GL, Lebel RR, Beg MB. Gastrointestinal manifestations in diploid/triploid mixoploidy. J Pediatr Gastroenterol Nutr. 2015; 60(6):799-801. https://pubmed.ncbi.nlm.nih.gov/25373857.
      4. Carson JC, Hffner L, Conlin L, et al. Diploid/triploid mixoploidy: A consequence of asymmetric zygotic Segregation of parental genomes. Am J Med Genet A. 2018; 176(12):2720-2732. https://pubmed.ncbi.nlm.nih.gov/30302900.
      5. Park S, Rho D, Lee HJ, et al. A case of pigmentary mosaicism associated with diploid/triploid mixoploidy. Int J Dermatol. 2018; 57(9):1120-1122. https://pubmed.ncbi.nlm.nih.gov/29624651.

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