Mucopolysaccharidoses Health Article

Definition

The mucopolysaccharidoses (MPS) are a number of metabolic disorders that follow a chronic and progressive course and involve many body systems.

Description

Though the symptoms and severity vary for each MPS disorder, common features include enlarged organs (organomegaly), dysostosis multiplex (abnormal bone formation), and a characteristic facial appearance. Hearing, vision, breathing, heart function, joint mobility, and mental capacity may also be affected. As of 2003, seven types of MPS have been classified. The MPS disorders are caused by absent or insufficient production of proteins known as lysosomal enzymes The specific enzyme that is deficient or absent distinguishes one type of MPS from another. However, before these enzymes were identified, the signs and symptoms expressed by an affected individual led to the diagnosis. The discovery of these enzymes resulted in a reclassification of some of the MPS disorders. These conditions are often referred to as MPS I, MPS II, MPS III, MPS IV, MPS VI, MPS VII, and MPS IX and may also referred to by their original names, which are Hurler (MPS I H), Hurler-Scheie (MPS I H/S), Scheie (MPS I S), Hunter (MPS II), Sanfilippo (MPS III), Morquio (MPS IV), Maroteaux-Lamy (MPS VI), Sly (MPS VII), and Hyaluronidase deficiency (MPS IX).

Demographics

The MPS syndromes are considered to be rare. Sanfilippo syndrome appears to be the most common MPS with a reported incidence of one in 70,000. The incidence of Hyaluronidase deficiency is not yet known. The incidence of the remaining six classes of MPS are estimated to be: one in 100,000 for Hurler syndrome; one in 500,000 for Scheie syndrome; one in 115,000 for Hurler/Scheie disease; one in 100,000 (male live births) for Hunter syndrome (mild and severe combined); one in 100,000 to one in 300,000 for Morquio syndrome (types A and B included); one in 215,000 for Maroteaux-Lamy syndrome; and less than one in 250,000 for Sly syndrome. These figures are general; more exact figures have been reported for individual MPS disorders in certain countries.