FAQs About Sanfilippo Syndrome

Emily Malcolm, PhD avatar

by Emily Malcolm, PhD |

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Sanfilippo syndrome — also called mucopolysaccharidosis type 3, or MPS 3 — is a progressive disorder that affects the brain and spinal cord, though other body systems also can be involved. It causes progressive intellectual disability and the loss of previously acquired skills.

Here are answers to some frequently asked questions about this rare disease.

What causes Sanfilippo syndrome?

Sanfilippo syndrome is caused by mutations in genes that encode for proteins involved in handling waste disposal in cells. Because of these mutations, cellular wastes build up in every cell, leading to the symptoms of the disease. It is unknown why the disease primarily affects the nervous system.

What are the types of Sanfilippo syndrome?

There are four subtypes of Sanfilippo syndrome, based on which gene is mutated in the patient. Despite being caused by mutations in different genes, the subtypes have similar symptoms.

Type A Sanfilippo syndrome is caused by mutations in the SGSH gene. People with this type of the disease do not produce an enzyme called heparan N-sulfatase.

Type B Sanfilippo syndrome occurs due to mutations in the NAGLU gene. In this disease subtype, patients do not make enough of an enzyme called alpha-N-acetylglucosaminidase.

Type C Sanfilippo syndrome is diagnosed when mutations are found in the HGSNAT gene. Those with Type C Sanfilippo do not produce enough of an enzyme called acetyl-CoA alpha-glucosaminide N-acetyltransferase.

Type D Sanfilippo syndrome is caused by mutations in the GNS gene. Patients with this type do not make enough of an enzyme called N-acetylglucosamine 6-sulfatase.

Each of these enzymes is responsible for a different step of breaking down a large sugar molecule called heparan sulfate.

How is Sanfilippo syndrome diagnosed?

Sanfilippo syndrome is diagnosed by a physical examination, enzyme tests in blood tests, and measurement of an undigested byproduct of heparin sulfate in urine (called GAGs).

However, to differentiate from other conditions that affect heparin sulfate processing, a genetic test looking for mutations in the GNSHGSNATNAGLU, and SGSH genes is required to confirm Sanfilippo syndrome. If doctors suspect your child may have Sanfilippo syndrome, they will ask for a small blood sample for genetic testing. The blood will be sent to a laboratory for the tests. It usually takes about three to six weeks to get the results.

Is Sanfilippo syndrome contagious?

Sanfilippo syndrome is not contagious. It cannot be passed from one person to another through physical contact.

Can Sanfilippo syndrome be inherited?

Sanfilippo syndrome is a genetic disorder that is inherited in an autosomal recessive manner, meaning that a patient must inherit two copies of a disease-causing mutation — one from each parent — in order to develop it. Parents normally have only one copy of the disease-causing mutation, making them carriers of the disease. Carrier parents usually do not have any symptoms of Sanfilippo syndrome. If both parents have a copy of a disease-causing mutation, their children have a 1 in 4 chance of inheriting two copies of such a mutation and developing Sanfilippo syndrome.

Parents of children with Sanfilippo syndrome, or a family history of relatives with the disease, should consider speaking with a genetic counselor. That would help the parents determine the risks of passing the disease on to their children, and let them know of any other options available.

What are the symptoms of Sanfilippo syndrome?

Patients generally do not show symptoms at birth, but begin having symptoms — such as delayed speech and behavior problems similar to autism spectrum disorder — in early childhood.

Some studies have indicated that some symptoms may be present in infancy – such as lung and airway abnormalities. Sleep disturbances are common in children with Sanfilippo syndrome. In later stages, people with the disease may have epileptic seizures or develop movement disorders.

The disease causes progressive intellectual disability and loss of learned skills, also called developmental regression. Those with the Sanfilippo syndrome also may have vision or hearing loss.

Is there a cure for Sanfilippo syndrome?

No cure is available yet for Sanfilippo syndrome, and not many treatments currently exist either. However, new treatments are under development. Three main strategies are being explored. One is modified enzyme replacement therapy, in which individuals are given the enzyme they lack in a modified form that can reach the brain and nervous system. Another strategy in development is gene therapy, in which the faulty gene in patients’ cells is replaced. Small molecule therapy, another strategy under development, aims to increase the activity of the defective enzyme.

Can children with Sanfilippo syndrome attend school?

Children with Sanfilippo syndrome can go to school, but may need additional accommodations because of their illness. Parents and caregivers should talk to school administration and develop an individualized education plan (IEP) for the student. An IEP establishes what accommodations the child will need and how the school will work with the student — and parents — to ensure all educational needs are met.

Where can I get more information?

We regularly publish articles on our website that covers Sanfilippo syndrome research, including new treatment options in development.

These organizations also offer information about Sanfilippo syndrome treatments and ongoing research:

Finally, we have two columns about the daily challenges of caring for patients with Sanfilippo syndrome:


Last updated: Oct. 28, 2019


Sanfilippo Syndrome News is strictly a news and information website about the disease. It does not provide medical advice, diagnosis or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.