Sanfilippo syndrome

Definition:

Sanfilippo syndrome is one of the hereditary mucopolysaccharide storage diseases, and it is characterized by the absence of one of several enzymes. These enzymes help the body get rid of a substance normally found outside of our cells called a mucopolysaccharide. This substance is called heparan sulfate, and in Sanfilippo syndrome, large amounts of it are excreted in the urine.

Alternative Names:

Mucopolysaccharidosis type III (subtypes A - B - C-D); Type IIIA = heparan sulfate sulfatase deficiency; Type IIIB = N-acetylglucosaminidase deficiency; Type IIID = N-acetylglucosamine-6-sulfate sulfatase deficiency

Causes, incidence, and risk factors:

Sanfilippo syndrome is transmitted as an autosomal recessive trait. It is possibly the most common of the mucopolysaccharide storage diseases. Sanfilippo syndrome has a relatively late onset rather than during the first year of life.

It shares, in common with most of the mucopolysaccharide storage diseases, coarse facial features, decreased mental development that progresses to severe mental retardation, stiff joints, gait disturbances, speech disturbances, and behavioral problems.

Unlike Hurler syndrome the cornea is clear, the condition is not as unrelenting, and survival times are longer, often into the twenties or later.

Symptoms:

Family history of Sanfilippo syndrome
May have normal growth during first few years, but final height is below average
Delayed development followed by deteriorating mental status
Deterioration of gait
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:

Hepatomegaly (liver enlargement)
Splenomegaly (spleen enlargement)
Corneas clear
Echocardiogram may show thickened heart
Abnormal bone x-rays such as thickened skull and oval vertebrae
Seizures, mental retardation
Activities of one of the above enzymes may be low in fibroblast skin cells
Urine may have increased heparan sulfate
Abnormal pathological staining character of white blood cells called metachromasia

Treatment:

There is no specific treatment for Sanfilippo syndrome. Specific complications may respond to conventional treatments as they arise.

Support Groups:

National MPS Society, Inc. 610-942-0100 www.mpssociety.org

Expectations (prognosis):

Severe retardation is the most important of the clinical problems. IQs may be below 50. Severe cases lead to death before 20 years of age.

In a minority of cases, Sanfilippo is compatible with a normal lifespan. The affected person may develop retinal degeneration leading to blindness, or may have seizures.

Complications:

Blindness
Seizures
Mental retardation
Progressive neurologic disease leading to becoming wheelchair bound
Inability to care for self

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.

Review Date: 10/23/2001
Reviewed By: David G. Brooks, M.D., Ph.D., Division of Medical Genetics, University of Pennsylvania Medical Center, Philadelphia, PA. Review provided by VeriMed Healthcare Network.

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