Type of disease: Rare conditions

Tetraploidy is a very rare condition where a baby has four copies of each chromosome. People have 23 distinct chromosomes, and normally, people only have two copies of each chromosome (46 total chromosomes). Babies with tetraploidy have four copies of each chromosome,for a total of 92 chromosomes. Since chromosomes contain the genetic information that tells our bodies how to grow and behave, having extra copies can cause serious growth and development problems. Tetraploidy usually causes a miscarriage very early on in pregnancy. Sometimes, the tetraploidy is not found in every cell and this is called diploid/tetraploid mosaic. This baby will have the normal two copies of chromsomes in some cells and four copies of chromosomes in other cells. Babies with diploid/tetraploid mosaic have severe mental and physical diabilities. There have been six reported cases of babies with non-mosaic tetraploidy (all of the baby’s cells have the abnormal four copies of every chromosome). Most died within a few days or months. Three lived past 12 months, with one living beyond 24 months (2 years). This little girl had facial abnormalities and severe developmental and growth delays as well as mutiple birth defects. The only way to determine if a baby has tetraploidy is to count the number of chromosomes using a karyotype, a medical test that looks at the chromosomes present in a person’s tissue sample (usually a blood sample or if suspected prenatally from a sample from a CVS or amniocentesis). Although there is currently no cure for tetraploidy, there are various resources to help manage the condition and treat birth defects. Talk with your baby’s doctor to decide on the best treatment plan for your baby. The risk of tetraploidy happening again in future pregnancies is believed to be low, but talking to a genetic counselor or specialist is the best way to get the most up to date information.

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