Definition of Sanfilippo syndrome:

Sanfilippo syndrome is an inherited disease of metabolism that makes the body unable to properly break down long chains of sugar molecules called glycosaminoglycans (formerly called mucopolysaccharides).

The syndrome belongs to a group of diseases called mucopolysaccharidoses (MPS). Specifically, it is known as MPS III.

See also:

• MPS I H (Hurler syndrome)
• MPS II, Hunter syndrome
• MPS IV (Morquio syndrome)
• MPS I S (Scheie syndrome)

Causes, incidence, and risk factors:

Sanfilippo syndrome occurs when the substances (enzymes) needed to break down the heparan sulfate sugar chain are missing or are defective.

There are four main types of Sanfilippo syndrome, also called MPS III. Which type a person has depends on which enzyme is affected.

• Sanfilippo type A is the most severe form. Persons with this type are missing or have an altered form of an enzyme called heparan N-sulfatase.
• Sanfilippo type B occurs when a person is missing or doesn't not produce enough alpha-N-acetylglucosaminidase.
• Sanfilippo C occurs when a person is missing or doesn't not produce enough acetyl-CoAlpha-glucosaminide acetyltransferase.
• Sanfilippo D occurs when a person is missing or doesn't not produce enough N-acetylglucosamine 6-sulfatase.

The syndrome is inherited as an autosomal recessive trait. That means both your parents must pass you the defective gene in order for you to get this disease.

Sanfilippo syndrome is possibly the most common forms of MPS. It is seen in about 1 in 70,000 births. A family history of Sanfilippo syndrome increases one's risk for this condition.