Mucopolysaccharidosis type IIIC
(MPS IIIC) 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 IIIC results from the missing or altered enzyme acetyl-CoAlpha-glucosaminide acetyltransferase. This condition is inherited in an autosomal recessive manner. There is no specific treatment. Most people with MPS IIIC live into their teenage years; some live longer. Source: Genetic and Rare Diseases Information Center (GARD), supported by ORDR-NCATS and NHGRI.