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Sanfilippo Syndrome


What Is Sanfilippo Syndrome?

Sanfilippo (san-fuh-LEE-po) syndrome is a rare genetic metabolism disorder. A change in a single gene makes a child's body unable to break down certain carbohydrates (sugars). This leads to serious problems in the brain and nervous system.

There is no cure yet for Sanfilippo syndrome. But doctors and researchers are working hard to find better treatments for it.

What Causes Sanfilippo Syndrome?

The body makes long chains of sugar molecules called glycosaminoglycans (GAGs), also called mucopolysaccharides. They:

  • help build cartilage, connective tissue, nerve tissue, and skin
  • help blood clot
  • are used in the communication between cells

The body continually builds GAGs and, when their job is done, breaks them down through metabolism.

One type of sugar molecule is called heparan sulfate. A child born with Sanfilippo has a defect in one of the genes that make enzymes needed to break down heparan sulfate. Without the gene, the used heparan sulfate builds up in the cells and keeps them from working as they should. This can damage organs, affecting growth, mental development, and behavior.

Four enzymes are involved in breaking down heparan sulfate, so there are four types of Sanfilippo syndrome (A, B, C, and D), depending on which enzyme is affected. Type A is the most common and most severe form.

A family history increases the risk for Sanfilippo syndrome, which affects about 1 in 70,000 births. The condition is also called mucopolysaccharidosis type III (MPS III).

What Are the Signs & Symptoms of Sanfilippo Syndrome?

Kids who have the condition are born with it. But most won't have symptoms until the preschool years, when they're between 2 and 6 years old. Then, they start to show developmental delays and behavioral issues. Trouble with sleep is common.

Early signs of Sanfilippo syndrome include:

  • speech and other developmental delays
  • getting many ear infections or sinus infections
  • large head size
  • respiratory infections
  • ongoing diarrhea
  • headaches
  • sleep problems
  • behavior issues that can look like those caused by autism
  • compulsive behaviors and hyperactivity

They get worse over time, leading to:

  • seizures
  • severe cognitive problems
  • progressive loss of motor skills (walking, speaking, feeding, etc.)

Sanfilippo syndrome affects life expectancy. Most children reach their teenage years, and some can live longer.

How Is Sanfilippo Syndrome Diagnosed?

Because it's so rare, it can take time for a child to be diagnosed with Sanfilippo syndrome. Doctors might suspect it when a child has:

  • significant behavioral problems
  • speech or developmental delays that get worse over time

A urine test to check for high levels GAGs in a child's pee can help confirm a diagnosis.

How Is Sanfilippo Syndrome Treated?

There is no cure yet for Sanfilippo syndrome. Treatment focuses on easing symptoms and giving a child the best quality of life for as long as possible.

But some tests and clinical trials (for instance, with enzyme replacement therapy and gene therapy ) have many doctors believing that help could be on the way.

What Else Should I Know?

Learning that a child has Sanfilippo syndrome can be overwhelming and upsetting for any family.

Turn to your child's care team for help and information. They're there to support your child and the whole family. You also can find support and information about Sanfilippo research online at:

Date reviewed: September 2019