1q21.1 Deletion

The information for this summary of 1q21.1 deletion syndrome comes from research publications. This is not meant to take the place of medical advice.

Click here for our full 1q21.1 deletion Gene Guide

The online Gene Guide includes more information about 1q21.1 deletion such as the chance of having another child with this condition, behavior and development concerns linked to 1q21.1 deletion or specialists to consider for people with this condition. Share this resource with family members or your clinical providers.

1q21.1 deletion syndrome is also called 1q21.1 microdeletion syndrome. For this webpage, we will be using the name 1q21.1 deletion syndrome to encompass the wide range of variants observed in the people identified.

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What is 1q21.1 deletion syndrome?

1q21.1 deletion syndrome happens when someone is missing a piece of chromosome 1, one of the body’s 46 chromosomes. Chromosomes are structures in our cells that house our genes.

Key Role

The 1q21.1 deletion region plays a role in brain development.

Symptoms

Because the 1q21.1 deletion region is important in brain development and function, many people who have 1q21.1 deletion syndrome have:

  • Low muscle tone
  • Global developmental delay
  • Intellectual disability
  • Small head size
  • Poor growth
  • Behavioral issues like aggression
  • Attention-deficit/hyperactivity disorder, or ADHD
  • Sleep issues
  • Autism 
  • Seizures
  • Vision issues, such as strabismus (crossed eyes) or nystagmus (repetitive uncontrolled eye movement)
  • Hearing loss
  • Joint laxity
  • Mild but nonspecific dysmorphic facial features

How many people have 1q21.1 deletion syndrome?

As of 2024, at least 153 people with 16p11.2 duplication syndrome have been identified in a medical clinic. The first case was found in 2008. There are likely many more undiagnosed people who have the syndrome.

Learn more about 1q21.1 Deletion and connect with other Simons Searchlight families with the resources below.

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Support Resources

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Genetic Information

What genes are involved in typical (Class 1) 1q21.1 deletions and duplications? In the “typical” 1q21.1 deletion or duplication, there are about 20 genes that are missing (deleted) or extra (duplicated). Some have not been researched at all, and have been left out of the summary. These genes that begin with “NBPF” have been found in children with features like macrocephaly, autism, schizophrenia, intellectual disability, congenital heart disease, neuroblastoma, and problems with the kidney and urinary tract. This gene family contains many pseudogenes (see definition below).

  • PRKAB2 – Important for regulating energy in cells (involved in making fatty acids and cholesterol for cells)
  • FMO5 – Two missing copies of this gene are associated with a condition called “Trimethylaminuria,” which causes an unusual odor.
  • GJA8 – Important for the growth of specific cells in the eye called “lens fiber cells.” Missing copies of this gene (deletions) can result in an increased chance for cataracts.
  • CHD1L – Important in chromatin remodeling (this is like “behind-the-scenes” work with preparing DNA to be used, read, or copied).
  • BCL9 – The function of this gene is unknown when it is deleted or duplicated in a person. Errors in this gene have been found in patients with B-cell acute lymphoblastic leukemia. The errors with this gene are thought to happen in a person’s cancer cells (which are usually genetically different than the cells in the rest of a person’s body. We do not think that people who have deletions or duplications of this gene are at an increased risk for leukemia.

What is a pseudogene? Pseudogenes are thought to be inactive gene. (“Pseudo” means “fake” in Latin.) They are similar to normal genes, but are not functional. The information or “genetic sequence” of a pseudogene is often similar to another gene that has a job in the body. Pseudogenes arise because of copying errors that have happened in the past. They are actually copies of other functioning genes, that were incorporated into a person’s DNA a very long time ago, but no longer have a job. Pseudogenes are considered “non-coding” DNA.

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GeneReviews

GeneReviews are a great resource to bring to your child’s clinicians. These publications provide a summary of current research on genetic conditions and information on ongoing care.

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Research Article Summaries

Below, we have summarized research articles about 1q21.1 Deletion. We hope you find this information helpful. The information available about 1q21.1 Deletion is limited, and families and doctors share a critical need for more information. As we learn more from children who have a change in this gene, we expect this list of resources and information to grow.

Full versions of published research articles can be found on PubMed. PubMed is a National Institutes of Health (NIH) online database that is free. It has a collection of both medical and scientific research articles. A PubMed search for 1q21.1 Deletion articles can be found here.

  • Clinical phenotype of the recurrent 1q21.1 copy-number variant Original research article by Bernier R. et al. (2016). Read the article here and the Simons Searchlight summary here. Read news coverage of the article here.
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Research Opportunities

Simons Searchlight Help the Simons Searchlight team learn more about 1q21.1 Deletion by taking part in our research. You can learn more about the project and sign up here.

External Research Opportunity: FaceMatch

FaceMatch is a platform that helps parents and doctors contribute to an international secure image database of both undiagnosed and diagnosed children across the globe. *This study is not affiliated with Simons Searchlight. Learn more about FaceMatch.

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Family Stories

Stories from 1q21.1 Deletion families:

Click here to share your family’s story.

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