15q26 overgrowth syndrome
What causes 15q26 overgrowth syndrome?
15q26 overgrowth syndrome is a chromosome disorder. Chromosomes contain our body's genetic information. Chromosomes are found in almost every cell of a person’s body. Human cells usually contain 46 chromosomes, or 23 pairs of chromosomes. One chromosome of each pair is inherited from our mother, and the other is inherited from our father. The first 22 pairs of chromosomes are numbered 1-22, and they are the same in males and females. The last pair are called the sex chromosomes and they determine our gender. Females have two X chromosomes (XX) and males have one X chromosome and one Y chromosome (XY).
Each chromosome is made up of 2 sections, called “arms” – a short arm and a long arm. The short arm of a chromosome is called the “p arm” while the long arm is called the “q arm”. The arms are broken down into even smaller sections which are designated by numbers. 15q26 overgrowth syndrome is a disorder caused when a person has too many copies of section 26 on the q arm of chromosome 15 – this is where “15q26” comes from. The condition is sometimes called “Tetrasomy 15q26 overgrowth syndrome”. “Tetra” means 4, and “somy” refers to the chromosomes. People with 15q26 overgrowth syndrome have four copies of the q26 section of chromosome 15 rather than the usual two.
A person's chromosomes are like the body's instruction manual. When a person has a extra chromosomal material, like in 15q26 overgrowth syndrome, it is like a section of the body's instruction manual is not correct. This causes problems with the normal development and functioning of the body. The two extra copies of 15q26 in patients with 15q26 overgrowth syndrome are what cause the symptoms of the condition. If someone is interested in testing to look for extra copies of 15q26, a genetics clinic would be the best type of medical team to coordinate this testing.
Levy B, Tegay D, Papenhausen P, Tepperberg J, Nahum O, Tsuchida T, Pletcher BA, Ala-Kokko L, Baker S, Ferederick B, Hirschhorn K, Warburton P, Shanske A. "Tetrasomy 15q26: a distinct syndrome or Shprintzen-Goldberg syndrome phenocopy?" Genetics in Medicine 2012. 14(9):811-818.