1q21.1 Deletion

Below is a summary for 1q21.1 Deletion observed in research publications. This is not meant to take the place of medical advice. Click HERE for the full gene guide, which includes more information, such as chance of having another child with this condition, or specialists to consider for people with this condition.

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What is 1q21.1 deletion syndrome?

People who have 1q21.1 deletion syndrome may have:

  • Developmental delay
  • Autism spectrum disorder
  • Mood disorders and anxiety
  • Short height
  • Cataracts, or a clouding in the lens of the eyes that affects vision
  • Heart problems

What causes 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. 

Do people who have 1q21.1 deletion syndrome look different?

People who have 1q21.1 deletion syndrome may look different. Some people have a small head, also called microcephaly.

How many people have 1q21.1 deletion syndrome?

As of 2020, doctors had described a few dozen people who have 1q21.1 deletion syndrome. The first case was found in 2008. There are likely many more undiagnosed people who have the syndrome. Scientists expect to find more people who have the syndrome as access to genetic testing improves.


Short height is found in 6 out of 12 people, or 50%.

Small head size is found in 4 out of 18 people, or 22%.




Tremors are found in 8 out of 18 people, or 44%.

Seizures are found in 3 out of 17 people, or 18%.




Low muscle tone is found in
7 out of 18 people, or 39%.

Overactive reflexes, also called hyperreflexia, is found in 6 out of 17 people, or 35%.

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


Support Resources


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.



Gene Reviews 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.

Check out the Gene Review for 1q21.1 Deletions here.


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.


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.


Family Stories

Stories from 1q21.1 Deletion families:

Click here to share your family’s story.