About MPS I

Mucopolysaccharidosis I (MPS I) is a rare, autosomal recessive disease with pathologic manifestations in most organ systems and tissues. The disease is caused by a defect in the gene coding for the lysosomal enzyme α-L-iduronidase; as a result, the cells of affected individuals are either unable to produce the enzyme or produce it in low amounts. This results in an inability of the lysosome to effect the stepwise degradation of certain glycosaminoglycans (GAGs) - namely dermatan sulfate and heparan sulfate - a process essential for normal growth and homeostasis of tissues.[1],[2],[3]

These GAGs, which are important constituents of the extracellular matrix, joint fluid and connective tissue throughout the body, progressively accumulate in the lysosome, ultimately causing cell, tissue and organ dysfunction by largely unknown pathophysiological mechanisms.

Even with similar levels of enzyme deficiency, patients with MPS I disease can experience a wide range of symptoms and variable degrees of severity.

Did You Know?

May 15th is International MPS Awareness Day. Join Sanofi Genzyme as we support raising awareness of MPS disease disorders and honoring the individuals and families who are affected.


  1. Clarke, L.A. (1997) Clinical diagnosis of lysosomal storage diseases. In: Organelle Diseases. Clinical Features, Diagnosis, Pathogenesis and Management. Applegarth, D.A., Dimmick, J.E., and Hall, J.G. (eds.). Chapman and Hall Medical, London.
  2. Clarke, L.A. and MacFarland, J. (2001) Mucopolysaccharidosis-I (MPS-I). The Canadian Society for Mucopolysaccharide and Related Diseases, Inc., Clarke, L.A., Kaweski, C., Di Ilio, L., and Hahn, S. (eds.). Ticky Graphics & Printing, Vancouver.
  3. Neufeld EF, Muenzer J. The Mucopolysaccharidoses. In: Valle D, Beaudet AL, Vogelstein B, Kinzler KW, Antonarakis SE, Ballabio A, Gibson K, Mitchell G. eds. The Online Metabolic and Molecular Bases of Inherited Disease New York, NY: McGraw-Hill; 2014. https://ommbid.mhmedical.com/content.aspx?bookid=971&sectionid=62642135. Accessed February 2019.