What Are The Symptoms

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 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.


  • 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
  • Umbilical hernia

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.


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

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