Sanfilippo syndrome is a rare, progressive, and fatal disease that affects 1 in 70,000 children. It is a genetic disorder that affects the metabolism of complex molecules and causes severe damage to the entire body, but most noticeably in the brain. Due to the lack of an enzyme, children with Sanfilippo have a problem with a chemical reaction that occurs naturally in the body.

Due to the lack of enzyme, large, complex sugar molecules (the heparan sulfates) cannot be broken down and recycled. Sanfilippo is a lysosomal storage disease. The heparan sulfate is stored in a part of the cell called the lysosome. It belongs to a group of diseases called mucopolysaccharidoses (MPS), which all involve the accumulation of complex sugar molecules (called mucopolysaccharides or glycosaminoglycans GAG). Another name for Sanfilippo is Mucopolysaccharidosis Type III or MPS III.

Sanfilippo primarily affects the brain and belongs to a group of diseases known as child dementia. Over time, brain cells fill up with waste that the body cannot excrete. The brain is increasingly damaged, the children with Sanfilippo suffer from severe hyperactivity, insomnia, speech loss, intellectual disability, heart problems, seizures, loss of mobility. All of this ultimately leads to death, usually long before adulthood.

How is Sanfilippo inherited?

Each of us inherited two copies of each gene, one from our mother and one from our father (with a few exceptions). Sanfilippo syndrome is an autosomal recessive hereditary disease. This means that a child with Sanfilippo received a faulty gene from each parent.  If both parents have a copy of the faulty Sanfilippo gene, then for any pregnancy there is a one in four chance of having a child with Sanfilippo.

Sanfilippo syndrome is a progressive disease. The children appear normal at birth and show no signs of the disorder. The first symptoms of the disease appear around the age of two to four years.