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Genetic and Rare Diseases Information Center (GARD)

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Mucopolysaccharidosis type III

Other Names for this Disease
  • Mucopoly-saccharidosis type 3
  • Sanfilippo syndrome
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Mucopolysaccharidosis type III (MPS III) is a genetic disorder that makes the body unable to break down large sugar molecules called glycosaminoglycans (GAGs, formerly called mucopolysaccharides).[1][2] Specifically, people with this condition are unable to break down a GAG called heparan sulfate.[2] Affected individuals can have severe neurological symptoms, including progressive dementia, aggressive behavior, hyperactivity, seizures, deafness, loss of vision, and an inability to sleep for more than a few hours at a time.[1] MPS III is inherited in an autosomal recessive manner.[2] There is no specific treatment for this condition.[2] Most people with MPS III live into their teenage years, and some live longer.[1] 

MPS III is divided into four subtypes, known as A, B, C and D.[1][2] Each subtype is caused by the alteration of a different enzyme needed to completely break down heparan sulfate. The different types of MPS III have similar signs and symptoms, although type A is the most severe.[1][2]

To view the GARD pages on the subtypes of MPS III, click on the following links:

Mucopolysaccharidosis type IIIA
Mucopolysaccharidosis type IIIB
Mucopolysaccharidosis type IIIC
Mucopolysaccharidosis type IIID

Last updated: 7/7/2011


  1. Mucopolysaccharidoses Fact Sheet. National Institute of Neurological Disorders and Stroke Website. February 16, 2010; Accessed 4/14/2010.
  2. Chambers D. Sanfilippo syndrome. Medline Plus Web site. May 11, 2009; Accessed 4/14/2010.
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  • The Online Mendelian Inheritance in Man (OMIM) is an catalog of human genes and genetic disorders. Each entry has a summary of related medical articles. It is meant for health care professionals and researchers. OMIM is maintained by Johns Hopkins University School of Medicine. 
  • Orphanet is a European reference portal for information on rare diseases and orphan drugs.  Access to this database is free of charge.
  • PubMed is a searchable database of medical literature and lists journal articles that discuss Mucopolysaccharidosis type III. Click on the link to view a sample search on this topic.

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