15q13.3 Deletion Syndrome

15q13.3 deletion syndrome happens when a person is missing a piece of chromosome 15, one of the body’s 46 chromosomes. Chromosomes are structures in our cells that house our genes. The missing piece can affect learning and how the body develops.

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 15q13.3 deletion 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 15q13.3 deletion syndrome, the sibling’s risk of having a child who has 15q13.3 deletion syndrome depends on the sibling’s genes and their parents’ genes. 

• If neither parent has the same genetic variant causing 15q13.3 deletion syndrome, the symptom-free sibling has a nearly 0 percent chance of having a child who would inherit 15q13.3 deletion syndrome. 
• If one biological parent has the same genetic variant causing 15q13.3 deletion 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 15q13.3 deletion syndrome, the risk of having a child who has the syndrome is about 50 percent.

As of 2024, more than 200 people with 15q13.3 deletion syndrome have been identified in a medical clinic. The first case of 15q13.3 deletion syndrome was described in 2008.

People who have 15q13.3 deletion syndrome may look different, but features are non-specific.

Scientists and doctors have only just begun to study 15q13.3 deletion 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 15q13.3 deletion 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

Depending on the specific 15q13.3 deletion, the 15q13.3 region may have up to seven genes deleted.

Speech and Learning

Just over one-half of people with 15q13.3 deletion syndrome had developmental delay or intellectual disability. Many people had speech delay.

• 74 out of 125 people had developmental delay or intellectual disability (59 percent)

Behavior

Some people with 15q13.3 deletion syndrome had behavioral disorders, including autism, attention-deficit/hyperactivity disorder (ADHD), poor attention span, mood disorder, and aggressive and/or impulsive behavior. Researchers think that about 1 in 10 people with 15q13.3 deletion syndrome might develop schizophrenia or mood disorders.

• 44 out of 125 people had a behavioral disorder (35 percent)
• 12 out of 125 people had autism (10 percent)
• 9 out of 125 people had ADHD (7 percent)
• 14 out of 125 people had schizophrenia (11 percent)
• 12 out of 125 people had a mood disorder (10 percent)

Brain

About 1 in 3 people with 15q13.3 deletion syndrome had seizures, most commonly absence seizures in childhood. Other seizure types included myoclonic absence, atonic seizures, and focal with impaired awareness. One small study suggested that the anti-seizure medication valproate was effective. Some people had brain changes observed on magnetic resonance imaging (MRI), such as brain cysts, hypoplasia, and dilation of certain brain regions.

• 37 out of 125 people had seizures (30 percent)

Other medical findings

Developmental issues varied widely from person to person with 15q13.3 deletion syndrome. Other medical issues included heart defects; vision issues; gastrointestinal issues; hypothyroidism or insulin-resistant diabetes; renal cyst (a narrowing of the tube that carries urine out of the body), and kidney stones.

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 15q13.3 deletion: www.simonssearchlight.org/research/what-we-study/15q13-3-deletion

• Simons Searchlight Facebook group: https://www.facebook.com/groups/15q13-3-deletion