Mucopolysaccharidosis, Type I (MPS I)



Mucopolysaccharidosis type I (MPS I) is an inherited condition that affects many different parts of the body. It is considered a lysosomal storage disorder because individuals with MPS I have lysosomes (the recycling center of each cell) that cannot break down certain types of complex sugars. This causes undigested sugar molecules and other harmful substances to build up in cells throughout the body, resulting in a variety of symptoms. Based on the current understanding of the enzyme and its gene, MPS I comprises a wide spectrum of severity and individuals may be categorized anywhere from severe to attenuated (less severe). Along with age of onset, the symptoms and long-term outcome within the spectrum of disease vary widely. For some babies with MPS I, detecting the condition early and beginning proper treatment may help prevent or delay some of the severe health outcomes associated with the condition. Babies with severe MPS I usually develop serious signs and symptoms in the first year of life and have a rapid disease progression. In the attenuated form of MPS I, symptoms are generally milder and do not appear until later in childhood. Early signs of MPS I include soft out-pouching around the belly-button or lower abdomen, large head, distinctive facial features that appear coarse, varying degrees of developmental delay and learning disabilities, swollen abdomen, clouding of the eye (corneal clouding), hearing loss, and frequent runny nose.

Condition Type:

Core Conditions


The severe form of mucopolysaccharidosis, type I (MPS I) affects approximately 1 in 100,000 babies worldwide. The less common and less severe form affects approximately 1 in 500,000 babies worldwide.

More Information for Parents:
Also known as:
  • MPS I
  • Alpha-L-iduronidase deficiency
  • Hurler-Scheie syndrome
  • Hurler syndrome
  • IDUA deficiency
  • Scheie syndrome
  • Mucopolysaccharidosis I
  • MPS I H-S

Core Conditions