Trisomy 18

[Renato]

Trisomy 18 is a chromosomal disorder caused by an extra chromosome 18 that results in intellectual disability and physical abnormalities.

Trisomy 18 caused by an extra chromosome 18.
Infants are typically small and have many physical abnormalities and problems with internal organs.
Tests can be done before or after birth to confirm the diagnosis.
There is no treatment available for trisomy 18.

(See also Overview of Chromosomal Disorders.)
Chromosomes are structures within cells that contain DNA and many genes. A gene is a segment of deoxyribonucleic acid (DNA) and contains the code for a specific protein that functions in one or more types of cells in the body (see Genes and Chromosomes for a discussion about genetics). Genes contain instructions that determine how the body is supposed to function.
An extra chromosome, making three of a kind (instead of the normal two), is called trisomy (see also Overview of Chromosome and Gene Disorders). Children who have trisomy 18 have a third chromosome 18. Trisomy 18 occurs in about 1 out of 6,000 live births. However, many affected fetuses spontaneously miscarry. The extra chromosome almost always comes from the mother. Mothers who are over age 35 are at increased risk of having a child with trisomy 18. There are more girls than boys with trisomy 18.

[Vania]

a rare and very serious genetic condition in which there is an additional copy of chromosome 18 in some or all of the bodys cells: