GENE GUIDE

HNRNPU-Related Syndrome

This guide is not meant to take the place of medical advice. Please consult with your doctor about your genetic results and health care choices. This Gene Guide was last updated on 2024. As new information comes to light with new research we will update this page. You may find it helpful to share this guide with friends and family members or doctors and teachers of the person who has HNRNPU-Related Syndrome.
a doctor sees a patient

HNRNPU-related syndrome is also called developmental and epileptic encephalopathy 54, or HNRNPU-related neurodevelopmental disorder (HNRNPU-NDD). For this webpage, we will be using the name HNRNPU-related syndrome to encompass the wide range of variants observed in the people identified. 

HNRNPU-related syndrome happens when there are changes in the HNRNPU gene. These changes can keep the gene from working as it should. 

Key Role

The HNRNPU gene plays a key role in the development of the brain. It is important in keeping people’s DNA organized in cells. 

Symptoms

Because the HNRNPU gene is important for brain activity, many people who have HNRNPU-related syndrome have: 

  • Developmental delay, or intellectual disability, or both 
  • Speech problems 
  • Autism spectrum disorder or features of autism 
  • Seizures 
  • Brain changes observed on magnetic resonance imaging (MRI)

HNRNPU-related 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 HNRNPU 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 HNRNPU plays a key role in development, de novo variants in this gene can have a meaningful effect.

Research shows that HNRNPU-related syndrome is often the result of a de novo variant in HNRNPU. Many parents who have had their genes tested do not have the HNRNPU genetic variant found in their child who has the syndrome. In some cases, HNRNPU-related syndrome happens because the genetic variant was passed down from a parent.

Autosomal dominant conditions

HNRNPU-related syndrome is an autosomal dominant genetic condition. This means that when a person has the one damaging variant in HNRNPU they will likely have symptoms of HNRNPU-related 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

GENE / gene
GENE / gene
Genetic variant that happens in sperm or egg, or after fertilization
GENE / gene
Child with de novo genetic variant
gene / gene
Non-carrier child
gene / gene
Non-carrier child

Why does my child have a change in the HNRNPU gene?

No parent causes their child’s HNRNPU-related syndrome. We know this because no parent has any control over the gene 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 gene change takes place on its own and cannot be predicted or stopped.

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 HNRNPU-related 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 HNRNPU-related syndrome, the sibling’s risk of having a child who has HNRNPU-related syndrome depends on the sibling’s genes and their parents’ genes.

  • If neither parent has the same genetic variant causing HNRNPU-related syndrome, the symptom-free sibling has a nearly 0 percent chance of having a child who would inherit HNRNPU-related syndrome.

As of 2024, over 140 people with HNRNPU-related syndrome have been identified in a medical clinic. 

People who have HNRNPU-related syndrome may look different. Appearance can vary and can include some but not all of these features: 

  • Larger than average eyebrows 
  • Larger than average nasal bridge 
  • Large space between the upper and lower eyelids 
  • Thin upper lip 
  • Short height

Scientists and doctors have only just begun to study HNRNPU-related 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 HNRNPU-related 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 major published articles. It highlights how many people have different symptoms. To learn more about the articles, see the Sources and References section of this guide.

Speech and Learning 

Most people with HNRNPU-related syndrome had developmental delay or intellectual disability, and 4 out of 5 people had speech delay. Many people were non-verbal. 

  • 75 out of 75 people had developmental delay (100 percent) 
  • 79 out of 89 people had intellectual disability (89 percent) 

Behavior  

One-half of people with HNRNPU-related syndrome had behavioral issues, including autism spectrum disorder or features of autism, obsessive-compulsive disorder, aggression, and attention issues. Some people had a very friendly personality. 

  • 28 out of 78 people had features of autism (36 percent)
36%
28 out of 78 people had features of autism.

Brain  

Most people with HNRNPU-related syndrome had seizures, which usually occurred before the age of 2 years old. Common seizure types included tonic–clonic and absence seizures. Almost one-half of people had seizures that are difficult to treat with medications, and they continued to have seizures even with treatment (called refractory epilepsy). 

Many people had low muscle tone (hypotonia) and/or brain changes observed on magnetic resonance imaging (MRI). Brain changes were usually non-specific and included enlargement of the ventricles of the brain and/or thinning of a region of the brain called the corpus callosum. 

  • 83 out of 88 people had seizures (94 percent) 
  • 52 out of 57 people had seizures before the age of 2 (91 percent) 
  • 19 out of 42 people had seizures that were refractory (45 percent) 
  • 36 out of 45 people had hypotonia (80 percent) 
  • 37 out of 64 people had brain changes on MRI (58 percent)
Human head showing brain outline
94%
83 out of 88 people had seizures.
91%
52 out of 57 people had seizures before the age of 2.
45%
19 out of 42 people had seizures that were refractory.
80%
36 out of 45 people had hypotonia.
58%
37 out of 64 people had brain changes on MRI.

Heart 

Almost 1 out of 3 people with HNRNPU-related syndrome had heart defects, most commonly a hole in the heart (atrial septal defect or ventricular septal defect) or an opening between two blood vessels leading from the heart (patent ductus arteriosus).  

  • 19 out of 62 people had heart defects (31 percent) 

Eyes  

The most common eye issue was crossed eyes (strabismus). 

  • 20 out of 57 people had vision issues (35 percent) 

 Muscle and skeletal findings 

 Rarely, people had muscle or skeletal features, such as relaxed joints or scoliosis (sideways curvature of the spine). 

 Other features 

 Many people with HNRNPU-related syndrome had feeding difficulties. Some people required a nasogastric tube (NG-tube) or a percutaneous endoscopic gastrostomy (PEG-tube) for feeding. 

 A few people had kidney issues, such as agenesis of the kidney, unilateral kidney, and renal pelviectasis (when urine gathers in the center of the kidney). 

  •  21 out of 37 people had feeding difficulties at birth (57 percent)

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.”

Sources and References

The content in this guide comes from a published study about HNRNPU-related syndrome. Below you can find details about the study, as well as a link to the full article.

  • Balasubramanian, M. HNRNPU-related neurodevelopmental disorder. 2022 Mar 10. In: Adam MP, Feldman J, Mirzaa GM, et al., editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2024. Available from: https://www.ncbi.nlm.nih.gov/books/NBK578573/ 
  • Rooney, K., van der Laan, L., Trajkova, S., Haghshenas, S., Relator, R., Lauffer, P., Vos, N., Levy, M. A., Brunetti-Pierri, N., … & Henneman, P. (2023). DNA methylation episignature and comparative epigenomic profiling of HNRNPU-related neurodevelopmental disorder. Genetics in Medicine, 25(8), 100871. https://pubmed.ncbi.nlm.nih.gov/37120726/
  • Taylor, J., Spiller, M., Ranguin, K., Vitobello, A., Philippe, C., Bruel, A. L., Cappuccio, G., Brunetti-Pierri, N., Willems, M., … & Balasubramanian, M. (2022). Expanding the phenotype of HNRNPU-related neurodevelopmental disorder with emphasis on seizure phenotype and review of literature. American Journal of Medical Genetics Part A, 188(5), 1497-1514. https://pubmed.ncbi.nlm.nih.gov/35138025/

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