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Sanfilippo syndrome

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 the first few years, but final height is below average. Delayed development is followed by deteriorating mental status.

Other symptoms include:

• Behavioral problems
• Coarse facial features
• Diarrhea
• Full lips
• Heavy eyebrows that meet in the middle of the face above the nose
• Sleep difficulties
• Stiff joints that may not extend fully
• Walking problems

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.

Support Groups

Additional information and resources are available from the National MPS Society.

Expectations (prognosis)

The syndrome causes significant neurological symptoms, including severe retardation. IQs may be below 50. Most persons with Sanfilippo syndrome live into their teenage years. Some patients live longer, while others with severe forms die at an earlier age. Symptoms appear most severe in persons with type A Sanfilippo syndrome.

Complications

• Blindness
• Inability to care for self
• Mental retardation
• Nerve damage that slowly gets worse and eventually requires wheelchair use
• Seizures

Calling your health care provider

Call your health care provider if your child does not seem to be growing or developing normally.

Call for an appointment with your health care provider if you plan to have children and you have a family history of Sanfilippo syndrome.

Prevention

Genetic counseling is recommended for prospective parents with a family history of Sanfilippo syndrome. Counseling is also recommended for families who have a child with Sanfilippo syndrome, to help them understand the condition and possible treatments.