About Sanfilippo

What is Sanfilippo Syndrome, and what causes it?

"It's difficult to explain to strangers why your 6 year old’s little sister is surpassing him in development..."

Tim & Valerie Byers, parents of Will

What Is Sanfilippo Syndrome?
Imagine Alzheimer’s, but in children.

In a nutshell, that’s what every family of children with Sanfilippo Syndrome faces.

Our children are born with a change in their DNA that causes a very important enzyme to be made improperly … or not at all.

Because they don’t have enough of this critical enzyme, our children cannot breakdown and recycle natural cellular waste. Their cells become clogged with toxic levels of heparan sulfate.

While every cell in the body is affected by Sanfilippo Syndrome, brain cells suffer the most. Sanfilippo’s effects on the brain become apparent between 2-6 years of age – speech problems, developmental delays, challenging behaviors, extreme hyperactivity, and poor sleep. All because of the build-up of cellular waste.

Many children are initially diagnosed with Autism before finding the underlying diagnosis of Sanfilippo Syndrome. Children with Sanfilippo go on to experience progressive dementia similar to Alzheimer’s, stealing away their skills and knowledge. Sanfilippo Syndrome will often cause these children to suffer from seizures. They will lose the ability to eat for themselves and many will get a feeding tube. They will lose the ability to walk and need a wheelchair. All because of Sanfilippo.

Relentless and devastating, children with Sanfilippo Syndrome often pass away in their teenage years.

Chart depicting progressive disability of Sanfilippo child compared to a neurotypical child

These videos help explain what Sanfilippo MEANS TO families living with it and a doctor working to cure it:

Saving Eliza

This is the story of Eliza O’Neill and her family… But it’s a story similar to the one all Sanfilippo families have experienced.

Our MPS Journey: The Jussop Family

This is the story of the Jessop family, which documents their oldest son Dylan’s journey with Sanfilippo Syndrome.

60 Minutes Interview

Professor John Hopwood, a doctor working to cure Sanfilippo Syndrome, explains the disease in this 60 Minutes interview.

Learn More About Sanfilippo SYNDROME:

What causes sanfilippo?

Sanfilippo Syndrome (also known as MPS III) is a rare, progressive, and fatal disease affecting 1 in 70,000 children. Sanfilippo is a genetic condition that affects the metabolism of complex molecules and results in severe damage to the entire body, but most significantly to the brain.

Individuals affected by Sanfilippo Syndrome lack an enzyme necessary to break down long chains of sugar molecules called mucopolysaccharides (also known as glycosaminoglycans or GAGs). As these molecules accumulate, the cellular machinery cannot work properly. Once enough of the toxic GAGs build up, the cells die and vital brain tissue is lost.

Sanfilippo is part of the MPS group of diseases.

MPS (Mucopolysaccharidosis) diseases are a part of the broader category of Lysosomal Storage Disorders (LSDs). The lysosome is a very small, but important, compartment in each cell. Enzymes in the lysosome are responsible for breaking down cellular material for recycling. A Lysosomal Storage Disorder is a disease where cellular materials doesn’t get recycled properly and instead accumulates in the cell, causing irreparable damage.

Mucopolysaccharides (MPS) are complex sugar molecules also known as GAGs (glycoaminoglycans) that are naturally produced by the body and used in the communication between cells, in blood clotting, and in the building of connective tissue, nerve tissue, and skin. As the body continuously produces these molecules, it also needs to continuously break them down after they are used.

Children with Sanfilippo Syndrome lack an enzyme required to break down the specific glycosoaminoglycan (GAG) called “heparan sulfate.”

There are four Types of Sanfilippo: Type A, B, C and D.

Each Sanfilippo subtype corresponds to a particular enzyme that is missing in the pathway that breaks down heparan sulfate. Type A is the most common form of Sanfilippo Syndrome, making up more than half of the cases. Sanfilippo Types B and C are less common, with Type D being the rarest form.

There can be significant variations in how quickly Sanfilippo progresses in each child, regardless of which subtype of the disease they have. Generally, children who are symptomatic and diagnosed with Sanfilippo Syndrome in the preschool years display a classic, severe progression of Sanfilippo’s effects. There are extremely rare instances where a child with Sanfilippo might not become symptomatic until they are teens or adults, and this is sometimes referred to as an “Attenuated” form of the disease, with a much slower progression.

Sanfilippo SYNDROME is an autosomal recessive genetic condition.

A genetic condition is one that is inherited (or passed down) from parents to child. For a child to have Sanfilippo Syndrome, they must have inherited one copy of the abnormal gene from EACH parent. Parents who carry one copy of the abnormal gene that causes Sanfilippo are called “Carriers.” This means that they are healthy, but silently “carry” the abnormal gene in their DNA.

Both boys and girls have an equal chance of having Sanfilippo Syndrome since the affected gene is not on the “sex” (X or Y) chromosome. Therefore, Sanfilippo is considered an “autosomal” condition.

A recessive condition like Sanfilippo Syndrome requires two copies of the abnormal gene to occur, one from each parent. Since Sanfilippo is a recessive, both likely-unknowing “Carrier” parents must pass their abnormal gene to the child for the disease to occur. If both parents are “Carriers” of an abnormal Sanfilippo gene, with each pregnancy, there is a 25% chance that the child will have the disease.
Sanfilippo is a PROGRESSIVE, NEURO-DEGENERATIVE, metabolic disorder.

Metabolism consists of a set of life-sustaining chemical reactions that are constantly occurring in all of our cells. Many of these reactions rely on enzymes to break down and process the substances our body use to stay healthy – like sugars, proteins, vitamins, and fats. In Sanfilippo Syndrome, the body does not have enough of the necessary enzymes to break down a special sugar called “heparan sulfate.”

What are the symptoms OF SANFILIPPO?

Children with Sanfilippo Syndrome appear healthy at birth and typically do not show obvious signs of the disease. However, even early on, many common childhood conditions are consistently seen in children with Sanfilippo Syndrome that are related to the disease. These can be easily (and incorrectly) dismissed and families are often reassured that the child “will grow out of it.”

It is necessary to look at the whole picture of what is going on with your child. If more than one of the following signs or symptoms are noted, it is important to consider checking for Sanfilippo Symdrome.

Early symptoms OF SANFILIPPO:
  • Speech delay
  • Recurrent ear/sinus infections
  • Large head size
  • Diarrhea/chronic loose stool
  • Poor sleep
  • Speech/developmental delays
  • “Autistic” behaviors
  • Significant hyperactivity
  • Respiratory issues at birth

Sanfilippo Syndrome is often diagnosed when parents notice their child missing developmental milestones, between ages 2 to 6, and undertake formal assessment. Because of its rarity, Sanfilippo remains largely unfamiliar to most medical practitioners. It is not uncommon that parents search for years to find the cause of their child’s difficulties before the correct diagnosis of Sanfilippo Syndrome is made. Sanfilippo can masquerade as ADHD (attention deficit hyperactivity disorder), autism, and intellectual disability. Because of this delay in finding the underlying diagnosis, many families have had other children born in the meantime … only to find out that they also have Sanfilippo Syndrome.

As Sanfilippo progresses, children typically develop extreme hyperactivity and behavioral problems. Sleep problems become so severe that they may not sleep for days or for only a few hours a night. They gradually lose all the abilities and skills they had acquired, such as speaking, walking, and the ability to eat by mouth.

Later features OF SANFILIPPO:
  • Progressive intellectual disability
  • Seizures
  • Enlarged liver/spleen
  • Prominent/thick eyebrows
  • Hearing loss (may occur earlier)
  • Loss of mobility – walking, running, sitting unsupported
  • Loss of ability to eat by mouth
  • Movement disorders, dystonia

What is the prognosis FOR SANFILIPPO?

Sanfilippo Syndrome has its most devastating effects on the brain. Children experience hyperactivity, sleeplessness, loss of speech, loss of toileting skills, intellectual disability, heart problems, vision loss, seizures, loss of mobility, dementia, and finally death.

The progression of Sanfilippo can vary significantly from one child to the next, making it particularly difficult to predict. Symptoms cover a wide spectrum and some children may experience particular symptoms more than others.

One special family created this video documenting their son’s life with Sanfilippo, particularly highlighting how the disease progressed over time.

SANFILIPPO does not yet have a cure … YET.

At this time, only supportive or “palliative” care is available for Sanfilippo Syndrome.

Life expectancy for children with Sanfilippo Syndrome is typically around 15 years.

For children living with Sanfilippo today, participation in a clinical trial is their only opportunity to try a treatment. Unfortunately, these trials only accept an extremely small number of patients.

Time is not something the children and families facing Sanfilippo have on their side. 

Medical research into Sanfilippo Syndrome has recently achieved promising break-throughs with real hopes for the future, but we are not there yet.

What should you do if you think your child has Sanfilippo?

First: contact your child’s doctor

If you think your child might have Sanfilippo Syndrome, immediately contact your pediatrician to have an evaluation and discuss your concerns.

Because Sanfilippo is a rare disease, your pediatrician or family doctor likely knows very little about it. You are your child’s best advocate. You have a right to seek the answers you need to help your loved one. Here’s a one-page Fact Sheet about Sanfilippo to take with you to the doctor to begin discussing your concerns. 

To test for Sanfilippo, request a “Urine MPS Screening” for your child, which detects whether heparan sulfate is present. Here’s detailed information about the Urine MPS Screening

The diagnosis of Sanfilippo may be confirmed by a blood test measuring the child’s enzymes. The enzyme assay is considered the most-credible diagnostic tool because it detects whether or not  enzymes in the cellular pathway that breaks down heparan sulfate are missing (the functional cause of Sanfilippo), providing a definitive answer. This test is also ideal for younger patients in which collecting a viable urine sample is difficult or impossible. Physicians can order a full enzyme assay blood test for Sanfilippo Syndrome, free of charge for eligible patients, at WhatWouldYouSuspect.com.


Second: contact us, we’re here

We are a community, a family of Sanfilippo families. There’s nothing like connecting with another parent who has walked the same path and understands the challenges you face. We’ll tell you all about Sanfilippo, share the latest research on Sanfilippo, tell you where clinical trials for Sanfilippo are happening, and how to start raising awareness about Sanfilippo. And most importantly, we’ll support you. Do not hesitate to contact us.

Cure Sanfilippo Foundation

501c3 non-profit
(Tax ID: 46-4322131)


P.O. Box 6901
Columbia, SC 29260