Mucopolysaccharidosis type IIIA
(MPS IIIA) is an genetic disorder that makes the body unable to break down large sugar molecules called glycosaminoglycans (GAGs, formerly called mucopolysaccharides). MPS IIIA is the most severe of the MPS III disorders and children with this condition have the shortest survival rate among those with the MPS III disorders. Individuals 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 IIIA is caused by the missing or altered enzyme heparan N-sulfatase. MPS IIIA is inherited in an autosomal recessive manner. There is no specific treatment for this condition. Source: Genetic and Rare Diseases Information Center (GARD), supported by ORDR-NCATS and NHGRI.