MPS I Hurler, Hurler Scheie and Scheie

Mucopolysaccharides are long chains of sugar molecules used in the building of bones, cartilage, skin, tendons and many other tissues in the body. “Muco” refers to the thick jelly-like consistency of the sugar molecules, “poly” means many, and “saccharide” is a general term for the sugar part of the molecule. In the course of normal life there is a continuous recycling process of building new mucopolysaccharides and breaking down old ones. The breakdown and recycling process requires a series of special biochemical tools called enzymes.

People with MPS I are missing or are low in an enzyme called alpha-L-iduronidase, which is essential in breaking down mucopolysaccharides dermatan sulphate and heparan sulphate. When dermatan sulphate and heparan sulphate are not completely broken down they remain stored in the body. The symptoms of MPS I occur when there is a build-up of dermatan sulphate and heparan sulphate in the tissues in the body. Babies may show little sign of the disease but as more and more cells build up with partially broken down mucopolysaccharides, symptoms start to appear.