Sanfilippo Syndrome and Autism

Page reviewed by: Dr. Cara O’Neill, FAAP
Page last updated: April 11, 2024
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Many children with Sanfilippo syndrome are first diagnosed with autism.

Often the parents feel the autism diagnosis “doesn’t quite fit” or “isn’t the whole answer” and they continue searching for more information. With additional testing, then the underlying cause of Sanfilippo is discovered.

Sometimes questions and confusion about the interplay of Sanfilippo and autism arise. The following is information about the two conditions and how they intersect.

Is autism a symptom of Sanfilippo?

Sanfilippo is one of the many genetic disorders that can be an underlying cause of autism. It is common for people with Sanfilippo to have both a diagnosis of Sanfilippo syndrome and autism.

To determine if your child also has autism, they will need formal testing by a child psychologist using a validated autism test (i.e., ADOS, CARS).

The importance of discovering the “why” behind autism diagnosis

Children who meet diagnostic criteria for autism, may be able to access additional therapies that could be helpful. For example, families of children with Sanfilippo and clinicians have found behavioral therapies such as ABA (Applied Behavioral Analysis) to be very helpful in improving challenging behaviors, facilitating communication and as a helpful technique for learning.

Typically, a formal autism diagnosis is required for insurance to consider covering behavioral therapy. Coverage and access to behavioral therapy services varies depending on your location in the US and around the world.

If your child is diagnosed with autism, a genetic evaluation is recommended by the American College of Medical Genetics. We encourage you to discuss the options with your doctors about what tests can be done to complete a medical evaluation for your child. You can talk with your primary care doctor and/or a specialist, such as a geneticist, neurologist or developmental pediatrician about your concerns.

Medical Evaluation of Autism

Genetic testing technology has advanced significantly since this 2013 publication. Whole exome or genome sequencing (WES or WGS) are now more commonly used tests. The utility of WES or WGS testing continues to grow as more and more cases of autism are linked to underlying genetic conditions.

Guidelines for Genetic testing in individuals with congenital anomalies, developmental delay, and intellectual disability

For individuals with congenital anomalies, developmental delay, and intellectual disability, genetic testing is recommended as part of routine medical evaluation for underlying causes of developmental delays, intellectual disability, and/or physical abnormalities at birth.

Is autism considered a misdiagnosis in the setting of Sanfilippo syndrome?

In previously published articles, autism has occasionally been referred to as a ‘misdiagnosis’ in Sanfilippo syndrome. In these same publications and as is widely accepted, behavioral symptoms of autism are common in individuals with Sanfilippo.

An autism diagnosis alone in a child who ultimately is found to have Sanfilippo syndrome would therefore be considered to be an ‘incomplete’ diagnosis rather than an ‘incorrect’ or ‘misdiagnosis’.

Once both conditions are diagnosed, they are considered to be co-occurring or co-morbid conditions that exist together. A diagnosis of Sanfilippo does not mean that the individual no longer has autism, it simply allows us to understand the root cause of the individual’s autism.

There are many genetic causes and conditions that are associated with syndromic autism (i.e. Fragile X, Rett syndrome, Down syndrome).

There is concern that if a child receives a diagnosis of autism and a thorough genetic testing evaluation is not performed, then the underlying cause of Sanfilippo or another condition may be missed. This is why a medical evaluation and consideration of genetic causes of autism is important for children and families.

What is syndromic vs. non-syndromic autism?

“Non-syndromic autism” is a category of autism where patients do not have other signs or symptoms associated with other medical conditions.

“Syndromic autism” is a category of autism where individuals do have signs or symptoms of another disease in addition to those associated with autism. These other symptoms may include epilepsy, developmental delay and regression, characteristic facial or physical features associated with other diseases, and more. Sanfilippo syndrome (all types) is associated with syndromic autism in many individuals.

Why is having both diagnoses important?

An autism diagnosis can open doors for children with Sanfilippo syndrome to receive additional services and supports that they might not otherwise be able to access. One example of these helpful services is Applied Behavioral Analysis therapy (ABA) that is an evidence based behavioral therapeutic approach widely accepted for the treatment of autism.

A co-occurring diagnosis of autism also provides families with a larger community to draw learnings from about how to navigate and support children with similar behavioral challenges.

Read more about Sanfilippo and ABA therapy:

Schreck, K.A., Helsel, C., Paxon, A. et al. Regression Trends & Treatment Effectiveness to Improve Quality of Life for a Pre-Adolescent Girl with MPS IIIA. J Dev Phys Disabil 30, 545–558 (2018).

Read more about Patient-centered Behavioral Therapy:

Do all lysosomal storage disorders co-occur with autism?

Many genetic metabolic diseases, also known as inborn errors of metabolism, are associated with autism. These include lysosomal diseases such as Sanfilippo syndrome, Batten disease, and Niemann-Pick disease type C. Emerging scientific discoveries continue and are bringing to light connections among rare and common diseases that weren’t thought of years ago.

A research project co-funded by Cure Sanfilippo Foundation and Sanfilippo Children’s Foundation (Australia) recently published its findings, “Altered heparan sulfate metabolism during development triggers dopamine-dependent autistic-behaviors in models of lysosomal storage disorders,” in the June 2021 edition of Nature Communications.

The work sheds light on a critical, but historically-understudied area – mechanisms behind the autism-related behaviors common in Sanfilippo. It is a new and interesting line of research that looks deeply at the mechanisms behind the behaviors of children with Sanfilippo. It also considers what types of drugs might be used to help not only treat the symptoms, but might preserve the neurological pathways in the dopamine system.

How does thinking about autism help develop treatments for Sanfilippo?

In the clinical trial of anakinra, funded and brought together by Cure Sanfilippo, an outcome measure designed for autism is being used as a clinical endpoint. Using outcome tools that are effective in autism studies can help us better measure the many co-existing neurobehavioral symptoms in Sanfilippo (sleep, agitation, stooling, engagement, etc.).

A new clinical trial, this time repurposing the drug epidiolex, will take place later this year, which also uses learnings from this treatment which is showing promise in studies of individuals with autism.

Are children with Sanfilippo a part of the autism community?

Yes. Many families find comfort in taking part in the autism community. The autism community being larger in population gives families more opportunities locally to connect to others and participate in events.