9q34 Duplication Syndrome
9q34 duplication syndrome is also called 9q34 microduplication syndrome. For this webpage, we will be using the name 9q34 duplication syndrome to encompass the wide range of variants observed in the people identified.
What is 9q34 duplication syndrome?
9q34 duplication syndrome happens when a person has an extra piece of chromosome 9, 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
The 9q34 region helps to control other genes during brain development.
Symptoms
Because the 9q34 region is important for brain activity, many people who have 9q34 duplication syndrome have:
- Developmental delay
- Intellectual disability
- Autism
- Hyperactivity
- Poor feeding
- Low muscle tone
- Speech and language issues
- Musculoskeletal defects
What causes 9q34 duplication syndrome?
9q34 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 genes from their mother, and from their father. In most cases, parents pass on exact copies of their genes 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 9q34 duplication plays a key role in development, de novo variants causing this duplication can have a meaningful effect.
Research shows that 9q34 duplication syndrome is often the result of a de novo variant. Many parents who have had their genes tested do not have the 9q34 duplication found in their child who has the syndrome. In some cases, 9q34 duplication syndrome happens because the genetic variant was passed down from a parent.
Autosomal dominant conditions
9q34 duplication syndrome is an autosomal dominant genetic condition. This means that when a person has the one damaging variant of the 9q34 duplication they will likely have symptoms of 7q11.23 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 does my child or I have 9q34 duplication syndrome?
No parent causes their child’s 9q34 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 9q34 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 9q34 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 9q34 duplication syndrome, the sibling’s risk of having a child who has 9q34 duplication syndrome depends on the sibling’s genes and their parents’ genes.
- If neither parent has the same genetic variant causing 9q34 duplication syndrome, the symptom-free sibling has a nearly 0 percent chance of having a child who would inherit 9q34 duplication syndrome.
- If one biological parent has the same genetic variant causing 9q34 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 9q34 duplication syndrome, the risk of having a child who has the syndrome is about 50 percent.
How many people 9q34 duplication syndrome?
As of 2024, over 35 people with 9q34 duplication syndrome have been identified in medical research. The first case was found in 1983. There are likely many more undiagnosed people who have the syndrome. This includes people with a small 9q34 duplication (only one gene duplicated), and people with large duplications (several genes duplicated).
Do people who have 9q34 duplication syndrome look different?
People who have 9q34 duplication syndrome may look different. Appearance can vary and can include some but not all of these features:
- Narrow opening of the eye
- Long face
- Small mouth
- Long, thin hands and feet
How is 9q34 duplication syndrome treated?
At this point, there are no medicines designed to treat 9q34 duplication 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
- Developmental 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 9q34 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: www.epilepsy.com/learn/types-seizures.
This section includes a summary of information from published articles. It highlights how many people have different symptoms. See the Sources and references section of this guide for a list of articles.
Behavior and development concerns linked to 7q11.23 duplication syndrome
The 9q34 duplication region differs from person to person and might have many genes duplicated. Some people inherit the 9q34 duplication from a parent who may or may not have medical features.
Speech and learning
Many people with 9q34 duplication syndrome had developmental delay and/or intellectual disability, usually mild delays. Fewer than one-half of people had speech delay.
- 26 out of 35 people had developmental delay or intellectual disability (74 percent)
- 15 out of 35 people had speech delay (43 percent)
Behavior
People with 9q34 duplication syndrome had behavioral issues, including autism, aggression, hyperactivity, attention-deficit/hyperactivity disorder (ADHD), or anxiety.
- 13 out of 35 people had autism (37 percent)
- 8 out of 14 people had other behavioral issues (57 percent)
Brain
Some people with 9q34 duplication syndrome had seizures or low muscle tone (hypotonia). Some people had sleep issues.
- 2 out of 15 people had seizures (13 percent)
- 2 out of 14 people had hypotonia (14 percent)
- 4 out of 10 people had difficulty sleeping (40 percent)
Medical and physical concerns linked to 9q34 distal deletion syndrome
Other medical features
Because of the small number of people described in the medical literature, it is unclear what other medical features are common for people with 9q34 duplication syndrome. Other medical features reported for one or two people with 9q34 duplication syndrome included low birthweight, being overweight, short height, and vision issues.
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 9q34 duplication: www.simonssearchlight.org/research/what-we-study/9q34-duplication
- Simons Searchlight 9q34 duplication Facebook community: https://www.facebook.com/groups/9q34-duplication
Sources and References
The content in this guide comes from published studies on 9q34 duplication syndrome. Below you can find details about each study, as well as links to summaries or, in some cases, the full article.
- Bonati, M. T., Castronovo, C., Sironi, A., Zimbalatti, D., Bestetti, I., Crippa, M., Novelli, A., Loddo, S., Dentici, M. L., … & Finelli, P. (2019). 9q34.3 microduplications lead to neurodevelopmental disorders through EHMT1 overexpression. Neurogenetics, 20(3), 145-154. https://pubmed.ncbi.nlm.nih.gov/31209758/
- Montanucci, L., Lewis-Smith, D., Collins, R. L., Niestroj, L. M., Parthasarathy, S., Xian, J., Ganesan, S., Macnee, M., Brünger, T., … & Lal, D. (2023). Genome-wide identification and phenotypic characterization of seizure-associated copy number variations in 741,075 individuals. Nature Communications, 14(1), 4392. https://pubmed.ncbi.nlm.nih.gov/37474567/
- Rots, D., Rooney, K., Relator, R., Kerkhof, J., McConkey, H., Pfundt, R., Marcelis, C., Willemsen, M. H., van Hagen, J. M., … & Kleefstra, T. (2024). Refining the 9q34.3 microduplication syndrome reveals mild neurodevelopmental features associated with a distinct global DNA methylation profile. Clinical Genetics, 105(6), 655-660. https://pubmed.ncbi.nlm.nih.gov/38384171/