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Reviewed May 2011
What is 15q13.3 microdeletion?
15q13.3 microdeletion is a chromosomal change in which a small piece of chromosome 15 is deleted in each cell. The deletion occurs on the long (q) arm of the chromosome at a position designated q13.3. This chromosomal change increases the risk of intellectual disability, seizures, behavioral problems, and psychiatric disorders. However, some people with a 15q13.3 microdeletion do not appear to have any associated features.
About half of all people with a 15q13.3 microdeletion have learning difficulties or intellectual disability, which is usually mild or moderate. Many of these individuals have delayed speech and language skills. 15q13.3 microdeletion also appears to be a major risk factor for recurrent seizures (epilepsy); about one-third of people with this chromosomal change have epilepsy.
15q13.3 microdeletion has also been associated with behavioral problems, including a short attention span, aggression, impulsive behavior, and hyperactivity. Some people with a 15q13.3 microdeletion have been diagnosed with developmental disorders that affect communication and social interaction (autism spectrum disorders). This chromosomal change may also be associated with an increased risk of psychiatric disorders, particularly schizophrenia. Other signs and symptoms of 15q13.3 microdeletion can include heart defects, minor abnormalities involving the hands and arms, and subtle differences in facial features.
Some people with a 15q13.3 microdeletion do not have any of the intellectual, behavioral, or physical features described above. In these individuals, the microdeletion is often detected when they undergo genetic testing because they have an affected relative. It is unknown why a 15q13.3 microdeletion causes cognitive and behavioral problems in some individuals but few or no health problems in others.
How common is 15q13.3 microdeletion?
15q13.3 microdeletion likely occurs in about 1 in 40,000 people in the general population. It appears to be more common in people with intellectual disability, epilepsy, schizophrenia, or autism spectrum disorders.
What are the genetic changes related to 15q13.3 microdeletion?
Most people with a 15q13.3 microdeletion are missing a sequence of about 2 million DNA building blocks (base pairs), also written as 2 megabases (Mb), at position q13.3 on chromosome 15. The exact size of the deleted region varies, but it typically contains at least six genes. This deletion usually affects one of the two copies of chromosome 15 in each cell.
The signs and symptoms that can result from a 15q13.3 microdeletion are probably related to the loss of one or more genes in this region. However, it is unclear which missing genes contribute to the specific features of the disorder. Because some people with a 15q13.3 microdeletion have no obvious signs or symptoms, researchers believe that other genetic or environmental factors may also be involved.
Read more about chromosome 15.
Can 15q13.3 microdeletion be inherited?
15q13.3 microdeletion is inherited in an autosomal dominant pattern, which means one copy of the deleted region on chromosome 15 in each cell is sufficient to increase the risk of intellectual disability and other characteristic features.
In about 75 percent of cases, individuals with 15q13.3 microdeletion inherit the chromosomal change from a parent. In the remaining cases, 15q13.3 microdeletion occurs in people whose parents do not carry the chromosomal change. In these individuals, the deletion occurs most often as a random event during the formation of reproductive cells (eggs and sperm) or in early fetal development.
Where can I find information about diagnosis or management of 15q13.3 microdeletion?
These resources address the diagnosis or management of 15q13.3 microdeletion and may include treatment providers.
General information about the diagnosis and management of genetic conditions is available in the Handbook. Read more about genetic testing, particularly the difference between clinical tests and research tests.
To locate a healthcare provider, see How can I find a genetics professional in my area? in the Handbook.
Where can I find additional information about 15q13.3 microdeletion?
You may find the following resources about 15q13.3 microdeletion helpful. These materials are written for the general public.
You may also be interested in these resources, which are designed for healthcare professionals and researchers.
What other names do people use for 15q13.3 microdeletion?
What if I still have specific questions about 15q13.3 microdeletion?
Where can I find general information about genetic conditions?
The Handbook provides basic information about genetics in clear language.
These links provide additional genetics resources that may be useful.
What glossary definitions help with understanding 15q13.3 microdeletion?
autism ; autosomal ; autosomal dominant ; cell ; chromosome ; deletion ; DNA ; expressivity ; genetic testing ; hyperactivity ; Mb ; microdeletion syndrome ; penetrance ; population ; reproductive cells ; schizophrenia ; spectrum ; sperm ; syndrome
You may find definitions for these and many other terms in the Genetics Home Reference Glossary.
See also Understanding Medical Terminology.
References (9 links)
The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? in the Handbook.