Information about trisomies and other genetic conditions
Many organizations offer education on genetic conditions such as Down syndrome and support to affected families. See below for a brief description of the genetic conditions that Harmony tests for.
Trisomy 21 (Down syndrome)
Down syndrome is a genetic condition that occurs when an extra chromosome (chromosome 21) originates in the development of either the sperm or the egg. When the egg and the sperm unite to form the fertilized egg, three (rather than two) chromosomes 21 are present.1 As the cells divide, the extra chromosome is repeated in every cell. This is why it’s referred to as “trisomy 21”. Down syndrome is the most frequently occurring chromosomal condition, occurring in about 1 in 700 births. Down syndrome can affect physical and intellectual development and may shorten lifespan.
Trisomy 18 (Edwards syndrome)
Trisomy 18 is due to an extra copy of chromosome 18. Trisomy 18 causes Edwards syndrome and is associated with a high rate of miscarriage. Infants born with Edwards syndrome may have various medical conditions and a shortened lifespan. It is estimated that Edwards syndrome is present in approximately one out of every 5,000 newborns.1
Trisomy 13 (Patau syndrome)
Trisomy 13 is due to an extra chromosome 13. Trisomy 13, also called Patau syndrome, is associated with a high rate of miscarriage. Infants born with trisomy 13 usually have severe congenital heart defects and other medical conditions. Survival beyond the first year is rare. It is estimated that trisomy 13 is present in approximately 1 out of every 16,000 newborns.1
Sex Chromosome Aneuploidies
Turner syndrome, in which a single intact X chromosome is present, affects 1 in 2,000 girls. Klinefelter syndrome, in which an extra X chromosome is present, affects 1 in 500-1000 boys. Other X and Y chromosome-related conditions affect as many as 1 in 650 newborns.
Socialstyrelsen Ovanliga diagnoser. Kromosomavvikelser, en översikt. (Including XXX and XXY)
Read more about the 22q11.2 deletion syndrome here or below.