Mucopolysaccharidosis type IIIB (MPS IIIB) is an genetic disorder that makes the body unable to break down large sugar molecules called glycosaminoglycans (GAGs, formerly called mucopolysaccharides).[950][951] Specifically, people with this condition are unable to break down a GAG called heparan sulfate.[951] 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.[950] MPS IIIB is caused by alterations (mutations) in the NAGLU gene. This gene provides the instructions for producing an enzyme called N-alpha-acetylglucosaminidase, which is needed to completely break down heparan sulfate. MPS IIIB is inherited in an autosomal recessive manner.[951] There is no specific treatment for this condition.[951] Most people with MPS IIIB live into their teenage years, and some live longer.[950]
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