HNRNPD-Related Syndrome

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

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

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

As of 2025, about 13 people in the world with an HNRNPD genetic variant have been identified in medical research.

People with an HNRNPD genetic variant may look different. Appearance can vary and can include, but are not limited to, these features:

• Ear defects or larger than average ears
• Rounder than average face

Scientists and doctors have only just begun to study HNRNPD-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 HNRNPD-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.

Speech and learning

Most people with HNRNPD-related syndrome had developmental delay or intellectual disability, gross and fine motor delay, and speech and/or language impairment.

• 10 out of 13 people had developmental delay or intellectual disability (77 percent)
• 8 out of 13 people had speech and/or language impairment (62 percent)

Behavior

People with HNRNPD-related syndrome had behavioral issues, such as autism, attention-deficit/hyperactivity disorder (ADHD), and aggressive, impulsive, or violent behavior.

• 6 out of 13 people had autism (46 percent)
• 2 out of 12 people had ADHD (17 percent)
• 4 out of 12 people had aggressive, impulsive, or violent behavior (33 percent)

Brain

Some people with HNRNPD-related syndrome had neurological medical issues, including seizures, lower than average muscle tone (hypotonia), a movement defect, and brain changes seen on magnetic resonance imaging (MRI).

• 2 out of 13 people had seizures (15 percent)
• 3 out of 12 people had hypotonia (25 percent)
• 5 out of 13 people had a movement defect (39 percent)
• 3 out of 12 people had brain changes seen on MRI (25 percent)

Other medical features

People with HNRNPD-related syndrome sometimes had feeding issues and/or gastrointestinal issues; genitourinary issues; vision issues; and ear defects.

• 4 out of 12 people had feeding difficulties and/or gastrointestinal issues (33 percent)
• 4 out of 13 people had genitourinary issues (31 percent)
• 4 out of 12 people had vision issues (33 percent)
• 3 out of 12 people had ear defects (25 percent)

HNRNP Family Foundation

The HNRNP Family Foundation is dedicated to improving the lives of patients and families around the world that live with rare HNRNP-Related Neurodevelopmental Disorders (HNRNP-RNDDs). They work closely with dedicated scientists and the medical community to drive patient-centered research. They are committed to finding treatments and creating a neurodiverse affirming ​community through education and support.  

• https://www.hnrnp.org/

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 HNRNPD – www.simonssearchlight.org/research/what-we-study/hnrnpd