Mucopolysaccharidosis type III (MPS III), also known as Sanfilippo syndrome, is a disorder that primarily affects the brain and spinal cord (central nervous system). It is characterized by deterioration of neurological function (neurodegeneration), resulting in many of the features of the condition. Other body systems can also be involved, although the physical features are usually mild in the early stages.

Variants (also called mutations) in the GNS, HGSNAT, NAGLU, and SGSH genes cause MPS III. These genes provide instructions for making enzymes involved in the breakdown of large sugar molecules called glycosaminoglycans (GAGs). GAGs were originally called mucopolysaccharides, which is where this condition gets its name. The GNS, HGSNAT, NAGLU, and SGSH enzymes are involved in the step-wise breakdown of a subset of GAGs called heparan sulfate.

MPS III is the most common form of mucopolysaccharidosis; the estimated incidence of all four types combined is 1 in 70,000 newborns. MPS IIIA and MPS IIIB are much more common than MPS IIIC and MPS IIID.

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have variants. The parents of an individual with an autosomal recessive condition each carry one copy of the altered gene, but they typically do not show signs and symptoms of the condition.

Published Date: November 07, 2022
Published By: National Institutes of Health