Definition
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)

Alternative Names
MPS III
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.

Symptoms
Unlike other forms of MPS, symptoms appear after the first year of life. A decline in learning ability typically occurs between ages 2 and 6. The child may have normal growth during first few years, but final height is below average. Delayed development is followed by deteriorating mental status.
Other symptoms include:
Walking problems
Coarse facial features
Full lips
Heavy eyebrows that meet in the middle of the face above the nose
Diarrhea
Stiff joints that may not extend fully

Signs and tests
A physical exam may show signs of liver and spleen swelling. An eye exam will show clear corneas, unlike the cloudy corneas seen in persons with Hurler syndrome (MPS I H). Neurological testing will reveal signs of seizures and mental retardation.
Urine tests will be done. Persons with Sanfilippo syndrome have large amounts of a mucopolysaccharide called heparan sulfate in the urine.
Other tests may include:
Blood culture
Echocardiogram
Slit lamp eye exam
Skin fibroblast culture
X-rays of the bones

Treatment
There is no specific treatment available for Sanfilippo syndrome