Chromosome 15q Duplication a.k.a. Dup15q Syndrome
What is chromosome 15q duplication?
Chromosome 15q duplication, which is also known as Dup15q syndrome, is a rare chromosome abnormality condition that occurs when an extra copy of the genetic material from the long arm (q) of chromosome 15 is present in each cell. Thus, the severity of the resulting condition is based on the size and location of the duplication and which particular genes are involved.
There are three main types of chromosome 15q duplications:
- Isodicentric Chromosome 15 (idic15): an extra chromosome made from two pieces of chromosome 15 that are stuck together end-to-end by their q arms; typically, there are two p arms, one on each end, and the amount of DNA that is included from the q arm can vary
- Interstitial Duplication/Triplication Chromosome 15 (int dup15/trp15): either one or two copies of part of chromosome 15q are inserted within the long arm of one of two copies of chromosome 15; the duplicated segment(s) is usually adjacent to the normal copy and can either be oriented in the same direction or opposite
- Micro duplications 11.2 and 13.3: small duplications located on chromosome 15q in the region 13.2-13.3, or the region 11.1-11.2, respectively
What causes chromosome 15q duplication?
Chromosome 15q duplication is caused by a sporadic mutation that occurs when the egg or the sperm is made. There is nothing that someone can do to prevent this duplication from occurring.
Occasionally, this duplication is passed down from parent to child, but the symptoms and their severity can vary significantly even between family members.
What are the symptoms of chromosome 15q duplication?
Though the signs and symptoms of chromosome 15q duplication vary greatly from case to case and are largely dependent on the size and location of the duplication, common features that are shared by many affected individuals include:
- Developmental delay and intellectual disability
- Low muscle tone (hypotonia)
- Genital abnormalities
- Distinctive facial features, such as high and/or cleft palate
- Feeding difficulties
- Slow growth
- Communication difficulties, behavioral, and/or emotional problems
- Abnormalities of the heart, kidney, and/or other organs
How is chromosome 15q duplication diagnosed?
There are several specialized tests available that can be used to confirm a diagnosis of a chromosome 15q duplication. These tests include:
- Karyotype to produce an image of a person’s chromosomes
- FISH to detect and locate a specific DNA sequence on a chromosome
- Array CGH to detect duplications that are too small to be visible on a karyotype
What are the available treatments for chromosome 15q duplication?
There is no cure currently available for chromosome 15q duplication, and since there is such a wide spectrum of related symptoms, treatment is symptomatic and supportive. It is important that this medical management is provided by a team of different specialists. For example, physical, speech, or occupational therapy can be used, and corrective surgery can be beneficial to treat certain physical abnormalities or congenital heart defects of the disorder, if present.