Definition:
Sanfilippo type B/MPS III B is caused by a mutated gene that manufactures alpha-n-acetylglucosaminidase, an enzyme needed in the process of breaking down a specific type of sugar or mucopolysaccharides. The enzyme, alpha-n-acetylglucosaminidase, is either produced in very low amounts or is completely absent in individuals afflicted with Sanfilippo type B/MPS III B. These sugars are used to build connective tissues in the body. Individuals affected with Sanfilippo type B/MPS III B have too many mucopolysaccharides in their system. An excessive amount of the sugars result in the clinical symptoms of Sanfilippo type B/MPS III B.

There are four types of Sanfilippo/MPS III: A, B, C, and D. There is very little clinical difference in the four different forms of this disorder. The differing characteristic is the mutation of the specific gene codes for the specific enzyme. The incidence of all four combined is estimated to be one in 70,000 births worldwide.

Symptoms:
Children born with Sanfilippo type B/MPS III B appear normal, but as cells become damaged, signs and symptoms associated with this disorder begin to appear. Symptoms are progressive and classified in stages based upon those presented. Behavioral problems associated with this disorder appear around two years of age.

In the initial stage, the affected child will display delayed speech skills as well as some mild facial abnormalities. In the following stage, the affected child will become extremely active, restless, suffer sleeplessness and exhibit difficult behavior. Many chew on their hands, clothes, or on other items. Over time, speech and comprehension will diminish. By age 10, the affected child’s movement will become very limited. In the final stage, the child affected with this disorder will become immobile and generally unresponsive.

Although most of the symptoms are neurological in nature, some children may also develop diaherra, cavities and an enlarged liver and spleen. Another phsyical chacteristic of this disorder is an abundance of coarse hair.

Inheritance Pattern:
Sanfilippo type B/MPS III B is an autosomal recessive disorder.

Life Expectancy:
Current life expectancy is 14 to 20 years of age.

Diagnois and Testing:
A urine test may be utilized to diagnose Sanfilippo type B/MPS III B. It measures increased levels of mucopolysaccharides, the type of sugar chain in the lysosome that accumulates as a result of the malfunctioning enzyme. A urine test is routinely followed by a blood test or skin biopsy, which will reveal reduced activity of the enzyme alpha-n-acetylglucosaminidase. Prenatal screening is available to examine alpha-n-acetylglucosaminidase activity in the fetus. Genetic testing is also available in combination with these diagnostic tests to look for the mutation that causes Sanfilippo type B/MPS III B.

Treatment:
There is no cure for Sanfilippo type B/MPS III B. If the disease is caught early, bone marrow transplant may slow down the progression of this disorder. In most cases, treatment is limited to reducing or controlling its symptoms. Medications to control the behavioral problems associated with this disorder have not been found to be effective. Anti-convulsant medication is often prescribed to control seizures, devices can be inserted in the mouth to aid swallowing, and wheelchairs are often required as the disorder progresses to its final and immobile stage. Genetic counseling is also encouraged.

Other potential treatments include enzyme replacement therapies that cross the blood-brain barrier, thereby treating neurological symptoms of the disease. It is recognized within the medical community that future treatment may be more effective following a diagnosis made early in the course of this disorder.

Patient Groups:
National MPS Society
4220 NC Highway 55, Suite 140
Durham NC, 27713
www.mpssociety.org
tel: (919) 806-0101
fax: (919) 806-2005
Barbara Wedehase, Executive Director
info@mpssociety.org