Mucopolysaccharidosis type IIID
(MPS IIID) is an genetic disorder that makes the body unable to break down large sugar molecules called glycosaminoglycans (GAGs, formerly called mucopolysaccharides). Specifically, people with this condition are unable to break down a GAG called heparan sulfate. 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. MPS IIID is caused by the missing or deficient enzyme N-acetylglucosamine 6-sulfatase. MPS IIID is inherited in an autosomal recessive manner. There is no specific treatment for this condition. Most people with MPS IIID live into their teenage years, and some live longer. Source: Genetic and Rare Diseases Information Center (GARD), supported by ORDR-NCATS and NHGRI.