Sanfilippo syndrome is metabolism disorder in which the body cannot properly break down long chains of sugar molecules. These chains of molecules are called glycosaminoglycans (formerly called mucopolysaccharides).
The syndrome belongs to a group of diseases called mucopolysaccharidoses (MPS). Specifically, it is known as MPS III.
Sanfilippo syndrome is an inherited condition, which means it is passed down through families. If both parents carry a nonworking copy of a gene related to this condition, each of their children has a 25% (1 in 4) chance of developing the disease. This is called an autosomal recessive trait.
Sanfilippo syndrome occurs when the substances (enzymes) needed to break down the heparan sulfate sugar chain are missing or defective.
There are 4 main types of Sanfilippo syndrome, also called MPS III. The type a person has depends on which enzyme is affected.
- Sanfilippo type A is the most severe form. People with this type do not have a normal form of the enzyme called heparan N-sulfatase.
- Sanfilippo type B occurs when a person is missing or does not produce enough alpha-N-acetylglucosaminidase.
- Sanfilippo C occurs when a person is missing or does not produce enough acetyl-CoAlpha-glucosaminide acetyltransferase.
- Sanfilippo D occurs when a person is missing or does not produce enough N-acetylglucosamine 6-sulfatase.
Symptoms often 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 worsening mental status.
Other symptoms include:
- Behavioral problems
- Coarse facial features
- 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
Exams 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 disability.
Urine tests will be done. People with Sanfilippo syndrome have large amounts of a mucopolysaccharide called heparan sulfate in the urine.
Other tests may include:
- Blood culture
- Genetic testing
- Slit lamp eye exam
- Skin fibroblast culture
- X-rays of the bones
There is no specific treatment available for Sanfilippo syndrome.
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The syndrome causes significant neurological symptoms, including severe mental disability. IQs may be below 50. Most people with Sanfilippo syndrome live into their teenage years. Some live longer, while others with severe forms die at an earlier age. Symptoms are most severe in people with type A Sanfilippo syndrome.
These complications can occur:
- Inability to care for self
- Mental disability
- Nerve damage that slowly gets worse and eventually requires wheelchair use
When to Contact a Medical Professional
Call your child's health care provider if your child does not seem to be growing or developing normally.
See your provider if you plan to have children and you have a family history of Sanfilippo syndrome.
Genetic counseling is recommended for couples who want to have children and who have 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. Prenatal testing is available.
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Spranger J. Mucopolysaccharidoses. In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 19th ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 82.
Wraith JE. Mucopolysaccharidoses and oligosaccharidoses. In: Saudubray J-M, van den Berghe G, Walter JH, eds. Inborn Metabolic Diseases: Diagnosis and Treatment. 5th ed. New York, NY: Springer; 2012:chap 40.
Reviewed By: Chad Haldeman-Englert, MD, FACMG, Wake Forest School of Medicine, Department of Pediatrics, Section on Medical Genetics, Winston-Salem, NC. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.