17q11.2 Duplication Syndrome
What is 17q11.2 duplication syndrome?
17q11.2 duplication syndrome happens when a person has an extra piece of chromosome 17, one of the body’s 46 chromosomes. Chromosomes are structures in our cells that house our genes. The extra piece can affect learning and how the body develops.
Key Role
Genes within the 17q11.2 region are important for brain development and function.
Symptoms
Because the 17q11.2 region is important for the proper function of the brain, some people may have:
- Failure to thrive
- Developmental delay
- Intellectual disability
- Large testicles in males
- Motor delay
- Speech delay
- Seizures
- Autism
- Smaller than average head size
- Low muscle tone
- Eye issues
What causes 17q11.2 duplication syndrome?
17q11.2 duplication syndrome is a genetic condition, which means that it is caused by variants in genes. Our genes contain the instructions, or code, that tell our cells how to grow, develop, and work. Every child gets two copies of the 17q11.2 gene: one copy from their mother’s egg, and one copy from their father’s sperm. In most cases, parents pass on exact copies of the gene to their child. But the process of creating the egg or sperm is not perfect. A change in the genetic code can lead to physical issues, developmental issues, or both.
Sometimes a spontaneous variant happens in the sperm, egg or after fertilization. When a brand new genetic variant happens in the genetic code is called a ‘de novo’ genetic variant. The child is usually the first in the family to have the genetic variant.
De novo variants can take place in any gene. We all have some de novo variants, most of which don’t affect our health. But because 17q11.2 plays a key role in development, de novo variants in this gene can have a meaningful effect.
Research shows that 17q11.2 duplication syndrome is often the result of a de novo variant in 17q11.2. Many parents who have had their genes tested do not have the 17q11.2 genetic variant found in their child who has the syndrome. In some cases, 17q11.2 duplication syndrome happens because the genetic variant was passed down from a parent.
Autosomal dominant conditions
17q11.2 duplication is an autosomal dominant genetic condition. This means that when a person has the one damaging variant in 17q11.2 they will likely have symptoms of 17q11.2 duplication syndrome. For someone with an autosomal dominant genetic syndrome, every time they have a child there is a 50 percent chance they pass on the same genetic variant and a 50 percent chance they do not pass on the same genetic variant.
Autosomal Dominant Genetic Syndrome
Why do I or my child have 17q11.2 duplication syndrome?
No parent causes their child’s 17q11.2 duplication syndrome. We know this because no parent has any control over the chromosome changes that they do or do not pass on to their children. Please keep in mind that nothing a parent does before or during the pregnancy causes this to happen. The genetic change takes place on its own and cannot be predicted or stopped.
What are the chances that other family members or future children will have 17q11.2 duplication syndrome?
Each family is different. A geneticist or genetic counselor can give you advice on the chance that this will happen again in your family.
The risk of having another child who has 17q11.2 duplication syndrome depends on the genes of both biological parents.
- If neither biological parent has the same genetic variant found in their child, the chance of having another child who has the syndrome is on average 1 percent. This 1 percent chance is higher than the chance of the general population. The increase in risk is due to the very unlikely chance that more of the mother’s egg cells or the father’s sperm cells carry the same genetic variant.
- If one biological parent has the same genetic variant found in their child, the chance of having another child who has the syndrome is 50 percent.
For a symptom-free brother or sister of someone who has 17q11.2 duplication syndrome, the sibling’s risk of having a child who has 17q11.2 duplication syndrome depends on the sibling’s genes and their parents’ genes.
- If neither parent has the same genetic variant causing 17q11.2 duplication syndrome, the symptom-free sibling has a nearly 0 percent chance of having a child who would inherit 17q11.2 duplication syndrome.
- If one biological parent has the same genetic variant causing 17q11.2 duplication syndrome, the symptom-free sibling has a 50 percent chance of also having the same genetic variant. If the symptom-free sibling has the same genetic variant, their chance of having a child who has the genetic variant is 50 percent.
For a person who has 17q11.2 duplication syndrome, the risk of having a child who has the syndrome is about 50 percent.
How many people have 17q11.2 duplication syndrome?
As of 2025, about 40 people with 17q11.2 duplication syndrome have been identified in medical research.
Do people who have 17q11.2 duplication syndrome look different?
People with 17q11.2 duplication syndrome may look different. Appearance can vary and can include some but not all of these features:
- Shorter than average height
- Smaller than average head size
- Long face
- Thin upper lip
- Early onset baldness
- Loss of tooth enamel
How is 17q11.2 duplication syndrome treated?
Scientists and doctors have only just begun to study 17q11.2 duplication syndrome. At this point, there are no medicines designed to treat the syndrome. A genetic diagnosis can help people decide on the best way to track the condition and manage therapies. Doctors can refer people to specialists for:
- Physical exams and brain studies
- Genetics consults
- Development and behavior studies
- Other issues, as needed
A developmental pediatrician, neurologist, or psychologist can follow progress over time and can help:
- Suggest the right therapies. This can include physical, occupational, speech, or behavioral therapy.
- Guide individualized education plans (IEPs).
Specialists advise that therapies for 17q11.2 duplication syndrome should begin as early as possible, ideally before a child begins school.
If seizures happen, consult a neurologist. There are many types of seizures, and not all types are easy to spot. To learn more, you can refer to resources such as the Epilepsy Foundation’s website: epilepsy.com/…t-is-epilepsy/seizure-types
This section includes a summary of information from major published articles and the Simons Searchlight quarterly registry report. It highlights how many people have different symptoms. To learn more about the articles, see the Sources and References section of this guide.
Behavior and development concerns linked to 17q11.2 duplication syndrome
The 17q11.2 duplication region differs from person to person and might have up to about 7 genes duplicated. Some people inherit the 17q11.2 duplication from a parent who may or may not have medical features.
Learning
Many people with 17q11.2 duplication syndrome had developmental delay and/or intellectual disability.
Behavior
People with 17q11.2 duplication syndrome had behavioral issues, such as autism.
Brain
Some people with 17q11.2 duplication syndrome had seizures, brain changes seen on magnetic resonance imaging (MRI), a smaller than average head size (microcephaly), or a larger than average head size (macrocephaly).
Medical and physical concerns linked to 17q11.2 duplication syndrome
Other medical features
Some people with 17q11.2 duplication syndrome had cleft lip and palate or were missing tissue in the eye (iris coloboma). People often had facial changes and/or failure to thrive.
Where can I find support and resources?
Simons Searchlight
Simons Searchlight is an online international research program, building an ever growing natural history database, biorepository, and resource network of over 175 rare genetic neurodevelopmental disorders. By joining their community and sharing your experiences, you contribute to a growing database used by scientists worldwide to advance the understanding of your genetic condition. Through online surveys and optional blood sample collection, they gather valuable information to improve lives and drive scientific progress. Families like yours are the key to making meaningful progress. To register for Simons Searchlight, go to the Simons Searchlight website at www.simonssearchlight.org and click “Join Us.”
- Learn more about Simons Searchlight: www.simonssearchlight.org/frequently-asked-questions
- Simons Searchlight webpage with more information on 17q11.2 duplication: www.simonssearchlight.org/research/what-we-study/17q11-2-duplication
- Simons Searchlight Facebook group: https://www.facebook.com/groups/17q11.2deletion
Sources and References
The content in this guide comes from published studies about 15q13.3 deletion syndrome. Below you can find details about each study.
- Chen, C. P. (2024). Prenatal diagnosis of familial 17q11.2 duplication encompassing NF1 in a pregnancy associated with asymptomatic carrier parent. Taiwanese Journal of Obstetrics and Gynecology, 63(3), 426-427. https://pubmed.ncbi.nlm.nih.gov/38802214/
- Grisart, B., Rack, K., Vidrequin, S., Hilbert, P., Deltenre, P., Verellen-Dumoulin, C., & Destrée, A. (2008). NF1 microduplication first clinical report: Association with mild mental retardation, early onset of baldness and dental enamel hypoplasia? European Journal of Human Genetics, 16(3), 305-311. https://www.nature.com/articles/5201978
- Martin, C. L., Wain, K. E., Oetjens, M. T., Tolwinski, K., Palen, E., Hare-Harris, A., Habegger, L., Maxwell, E. K., Reid, J. G., … & Ledbetter, D. H. (2020). Identification of neuropsychiatric copy number variants in a health care system population. JAMA Psychiatry, 77(12), 1276-1285. https://pubmed.ncbi.nlm.nih.gov/32876661/
- Moles, K. J., Gowans, G. C., Gedela, S., Beversdorf, D., Yu, A., Seaver, L. H., Schultz, R. A., Rosenfeld, J. A., Torchia, B. S., & Shaffer, L. G. (2012). NF1 microduplications: Identification of seven nonrelated individuals provides further characterization of the phenotype. Genetics in Medicine, 14(5), 508-514. https://www.gimjournal.org/article/S1098-3600(21)04228-3/fulltext
- Goh, S., Thiyagarajan, L., Dudding-Byth, T., Pinese, M., & Kirk, E. P. (2025). A systematic review and pooled analysis of penetrance estimates of copy-number variants associated with neurodevelopment. Genetics in Medicine, 27(1), 101227. https://pubmed.ncbi.nlm.nih.gov/39092588/