The mucopolysaccharidoses (MPS) are a group of inherited diseases, each caused by a different enzyme deficiency. Seven distinct clinical types and numerous subtypes of the mucopolysaccharidoses have been identified. They are named after the doctor who first identified them.
In addition to MPS I, the MPS family of diseases include:
- MPS II, Hunter syndrome, is caused by lack of the enzyme iduronate sulfatase. MPS II occurs in males, and females may be carriers of the gene for MPS II. Although rare, MPS II has been diagnosed in females. The incidence of Hunter syndrome is estimated to be ~ 1:100,000 to ~ 1:170,000 male births.
- MPS III, Sanfilippo syndrome is caused by a deficiency of a different enzyme needed to completely break down the heparan sulfate sugar chain. There are four distinct types of Sanfilippo syndrome: Sanfilippo A, Sanfilippo B, Sanfilippo C, and Sanfilippo D. There have been some cases of the B form where the affected individuals have remained relatively healthy into adult life.
- MPS IV, Morquio syndrome, results from the missing or deficient enzymes N-acetylgalactosamine 6-sulfatase or beta-galactosidase needed to break down the keratan sulfate sugar chain. Babies may show little sign of the disease, but as more and more cells become damaged, symptoms start to appear.
- MPS VI, Maroteaux-Lamy syndrome, is caused by the deficient enzyme N-acetylgalactosamine 4-sulfatase. Over time, more cells become damaged and symptoms begin to appear. It has been estimated that about 1 in 215,000 births are affected with MPS VI.
- MPS VII, Sly syndrome, is caused by deficiency of the enzyme beta-glucuronidase. Over time, more cells become damaged and symptoms begin to appear. As one of the least common forms of the mucopolysaccharidoses, it is estimated to occur in fewer than 1:250,000 births.
- MPS IX is a rare disorder that results from hyaluronidase deficiency. It is characterized by short stature, soft-tissue masses and normal joint movement and intelligence.