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Genetic and Rare Diseases Information Center (GARD)

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Diploid-triploid mosaicism

Other Names for this Disease
  • Diploid/triploid mixoploidy
  • Diploid/triploid mosaicism
  • Growth retardation, truncal obesity, facial asymmetry, hypotonia, small phallus, malformed low-set ears and micrognathia
  • Mosaic triploidy
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Your Question

My young daughter has a rare genetic condition called diploid-triploid mosaicism. I am looking for any and all available information about this disorder. It is very rare and therefore it is very hard to find information that is of much use. Anything will help at this point.

Our Answer

We have identified the following information that we hope you find helpful. If you still have questions, please contact us.

What is diploid-triploid mosaicism?

Diploid-triploid mosaicism is a chromosome disorder.  Individuals with diploid-triploid syndrome have some cells with three copies of each chromosome for a total of 69 chromosomes (called triploid cells) and some cells with the usual 2 copies of each chromosome for a total of 46 chromosomes (called diploid cells).  Having two or more different cell types is called mosaicism. Diploid-triploid mosaicism can be associated with  truncal obesity, body/facial asymmetry, weak muscle tone (hypotonia), delays in growth, mild differences in facial features, fusion or webbing between some of the fingers and/or toes (syndactyly) and irregularities in the skin pigmentation.[1]   Intellectual disabilities may be present but are highly variable from person to person ranging from mild to more severe.[2]  The chromosome disorder is usually not present in the blood; a skin biopsy, or analyzing cells in the urine is needed to detect the triploid cells. [1][2][3]
Last updated: 3/22/2010

What are the signs and symptoms of diploid-triploid mosaicism?

The signs and symptoms associated with diploid-triploid mosaicism can include facial and body assymmetry, growth delays, decreased muscle tone (hypotonia), limb differences (such as syndactyly of 3rd and 4th fingers of the hands and/or 2nd and 3rd toes; clinodactyly, and/or camptodactyly usually of the 5th finger), minor differences in facial features and intellectual disabilities of variable degrees ranging from very mild[2] to severe.    Truncal obesity and irregular pigmentation of the skin can develop usually later in life. [1][2]
Last updated: 3/22/2010

How is diploid-triploid mosaicism diagnosed?

For most individuals with diploid-triploid mosaicism, the triploid cells are restricted to certain tissues.  Most often, the triploid cells are not detected in a chromosome analysis (karyotype) of the blood.  The cells may only be detected in skin fibroblasts.  Thus, the diagnosis may only be confirmed by a skin biopsy or the investigation of urinary cells. [1][2][3]
Last updated: 3/22/2010

  • van de Laar, I; Rabelink, G.; Hochstenbach R.; Tuerlings, J.; Hoogeboom, J.; Giltay, J.. Diploid triploid mosaicism in dysmorphic patients. Clinical Genetics. July 26, 2002; Accessed 1/1/1900.
  • 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; Accessed 1/1/1900.
  • Gardner and Sutherland. Chromosome Abnormalities and Genetic Counseling, 3rd Edition. NY, NY: Oxford University Press; 2004;