What is Sanfilippo Syndrome?

Imagine Alzheimer’s, but in children.

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

Sanfilippo Syndrome (also known as Mucopolysaccharidosis III) is a terminal, neurodegenerative rare disease. It causes children to lose all the skills they’ve gained, suffer seizures and movement disorders, experience pain and suffering, and then die, often before the second decade of life.

Because of its neurodegenerative nature and multi-system impact, Sanfilippo Syndrome is often called "childhood Alzheimer's."

Currently there is no FDA-approved treatment or cure.

There are subtypes of Sanfilippo Syndrome

Four subtypes of Sanfilippo have been identified - Types A, B, C, and D. Each corresponds to a particular enzyme that is missing or not working properly in the body’s process of breaking down heparan sulfate.

In most of the world, Type A is the most common subtype, making up more than half of the cases. Types B and C are less common, and Type D is the rarest.

Type A is typically considered the most-severe subtype of Sanfilippo. This means that most people with Type A have a rapidly-progressing form with earlier loss of abilities, such as talking and walking, and an earlier age of death. Type B may progress somewhat less rapidly, on average. Types C and D have more variable progression rates, but most persons tend to retain skills longer than in A and B.

Learn more about the symptoms, how to get diagnosed, prognosis, current research, and more below.

Figure depicting progressive disability of Sanfilippo Syndrome in child compared to a neurotypical child

One family's story

This video is the story of Eliza O’Neill and her family. It’s a story similar to the one every Sanfilippo families experiences. Please take a moment to watch.

What Causes Sanfilippo Syndrome?

Children with Sanfilippo Syndrome are born with a single gene defect, a single change in their DNA, that causes their bodies to lack a necessary enzyme. Because of the lack of enzyme, their bodies are unable to breakdown heparan sulfate, a natural cellular waste. Instead, their bodies and particularly brains become clogged with toxic levels, which causes a cascade of detrimental effects and ultimately death.

What Are the Symptoms and Prognosis?

Signs of Sanfilippo can be present in the newborn period of a child's life, but often go unnoticed without newborn screening. Most symptoms typically begin to be recognized between 1 and 6 years of age when the child begins showing signs of developmental delay.

Relentless and devastating, Sanfilippo has 100% mortality rate, with children typically passing away in their early teens.

How Is Sanfilippo Syndrome Diagnosed?

It often takes years to receive a correct diagnosis of Sanfilippo Syndrome. Due to its rarity and lack of physician awareness, a child’s symptoms are often classified as developmental delay and/or Autism until a thorough medical workup is done to identify the underlying cause. Learn about the options for getting your child screened for Sanfilippo.

Where Does Research For a Cure Stand?

Today, there is no FDA-approved treatment or cure for Sanfilippo Syndrome. Clinical trials are happening, and other treatment strategies are in pre-clinical research and require funding.

Has Your Child Been Diagnosed with Sanfilippo?

If your child has been diagnosed with Sanfilippo or is currently awaiting testing, we are here for you. Contact us to learn more, get expert answers to your questions, and explore current research and clinical trial options that may be available.

This page's content has been medically reviewed by Dr. Cara O'Neill, FAAP.

Help Simon - Simon's parents looking at him