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, brain cells suffer the most. Effects on the brain become apparent between 2-6 years of age – speech problems, developmental delays, challenging behaviors, extreme hyperactivity, and poor sleep.

Many children are initially diagnosed with Autism before finding the underlying diagnosis. Children will go on to experience progressive dementia similar to Alzheimer’s, stealing away their skills and knowledge.  Children will often 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. 

Children often pass away in their teenage years.  It is relentless and devastating.

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, one of the doctors 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 progressive and fatal disease affecting 1 in 70,000 children. It 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 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, making up more than half of the cases. Types B and C are less common, with Type D being the rarest form.

There can be significant variations in how quickly the disease progresses in each child, regardless of which subtype of the disease they have. Generally, children who are symptomatic and diagnosed in the preschool years display a classic, severe progression of Sanfilippo’s effects. There are extremely rare instances where a child 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 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 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. Every person has 23 pairs of chromosomes, 22 of which are “autosomal,” meaning they do not determine your gender. Therefore, Sanfilippo is considered an autosomal condition.

A recessive condition like Sanfilippo requires two copies of the abnormal gene to cause the disease, one from each parent. Since Sanfilippo is a recessive condition, 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?

Children at birth appear healthy 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 that are related to the disease. These can be easily 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.

Early symptoms:
  • 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

The disease is often diagnosed when parents find their child missing developmental milestones, between ages 2 to 6, and undertake formal assessment. Because of its rarity, the disease 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 a correct diagnosis 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 their younger children are also affected with the disease.

As Sanfilippo progresses, children will 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 per 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:
  • 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?

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 disease progression 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, which documents their son’s journey living with Sanfilippo, particularly highlighting how the disease progressed in their son over time.

The disease does not yet have a cure … YET.

At this time, only supportive or “palliative” care is available. Life expectancy 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, and time is not something these children have on their side. Medical research 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. Request a “Urine MPS Screening.” Here’s detailed information about the Urine MPS Screening

Because Sanfilippo is a rare disease, your pediatrician or family doctor may not have ever heard of it. You, like every parent, 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. 

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, where the research is, where things stand, and how to start raising awareness. And most importantly, we’ll support you. So please do not hesitate to contact us.

Cure Sanfilippo Foundation

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


P.O. Box 6901
Columbia, SC 29260