What is trisomy 20p?
Trisomy 20p is a rare genetic condition. It causes intellectual disability and delayed motor milestones, such as walking.
Humans usually have 23 pairs of chromosomes. In each pair, one chromosome copy comes from the mother and one copy comes from the father. Altogether, there are usually 46 chromosomes. Each pair is numbered 1 through 22 except for the sex chromosomes, which are labeled “X” and “Y.” Females have two X chromosomes. Males have one X chromosome and one Y chromosome.
Each chromosome has a center with two arms coming out of it. The arms are different lengths. One arm is short and is called the "p" arm. The other arm is long and is called the "q" arm.
In trisomy 20p, there is an extra copy of the short arm (the "p" arm) of chromosome 20 in the cells of the body. This is called a "trisomy" because there are three copies instead of the usual two copies of chromosome 20p.
An extra chromosome 20p can cause a range of symptoms. These include certain facial features, bone problems, heart defects, and abnormal kidneys. Children with trisomy 20p usually reach milestones, like walking, later than other children. They also have intellectual disability and may need to be in special classes. Children with trisomy 20p usually grow at a normal rate. They will not be significantly shorter or taller than other children their age. The symptoms can be more or less severe. This depends on how much of chromosome 20p is added. Usually, having more of the chromosome will result in more serious symptoms. Less than 40 patients with trisomy 20p have been described in the literature.
SOURCE: Emory University - Department of Human Genetics in collaboration with ThinkGenetic • https://www.thinkgenetic.com/diseases/trisomy-20p/overview/7413 • DATE UPDATED: 2016-06-08