MPS I – Hurler, Hurler Scheie and Scheie
For further information please download our Guide to MPS I.
What is MPS I?
This is one of the Mucopolysaccharide storage diseases. MPS I is also known as Hurler disease. Hurler disease takes its name from Gertrud Hurler, the doctor who first described a boy and girl with the condition in 1919. In 1962, Dr Scheie, a consultant ophthalmologist, identified a patient with an attenuated (less severe) form of MPS I. Patients who appear not to fit clearly at either end of the spectrum are classified with Hurler Scheie disease. Hence, MPS I is also called Hurler (MPS IH), Hurler-Scheie (MPS IHS) and Scheie (MPS IS) diseases.
MPS I comprises a wide spectrum of severity and the traditional classification of Hurler, Hurler Scheie and Scheie does not adequately reflect the wide spectrum.
Although there is no cure for MPS diseases, there are ways of managing and treating the problems they cause.
What causes this disease?
Mucopolysaccharides are long chains of sugar molecule used in the building of connective tissues in the body.
- “saccharide” is a general term for a sugar molecule (think of saccharin)
- “poly” means many
- “muco” refers to the thick jelly-like consistency of the molecules
There is a continuous process in the body of replacing used materials and breaking them down for disposal. Individuals with MPS I disease are missing an enzyme called alpha-L-iduronidase which is essential in breaking down the mucopolysaccharides called dermatan sulfate and heparan sulfate. The incompletely broken down mucopolysaccharides remain stored in cells in the body causing progressive damage. Babies may show little sign of the disease, but as more and more cells become damaged, symptoms start to appear.
Does MPS I affect individuals differently?
MPS I comprises a wide spectrum of severity and clinical involvement. Children with the classic, severe form of Hurler disease have progressive developmental delay, severe progressive physical problems and early advancement of the disease. Children and adults with Scheie disease do not have progressive developmental delay and their physical problems advance more slowly. There are others whose disease pattern will fall between the two ends of the spectrum. It is important to remember that MPS I is extremely varied in its effects.
How common are these diseases?
The MPS Society, which coordinates the Registry for Mucopolysaccharide and related diseases, has shown that MPS I is a rare condition affecting approximately 1 in 100,000 live births. In the UK, between 1989 and 1999, 68 babies were born with MPS IH, 16 were born with MPS IHS and 4 were born with MPS IS.
How is the disease inherited?
MPS I is an autosomal recessive disease whereby both parents must carry the same defective gene and each pass this same defective gene to their child. Where both parents are carriers of the MPS I gene there is a 25% (1:4) chance of having an affected child in each pregnancy. There is a 50% (1:2) chance of a child receiving only one copy of the defective gene and therefore being a carrier. A carrier will not be affected but can pass the defective gene to his/her offspring. The remaining 25% (1:4) will be neither affected nor a carrier. Using information from an affected individual’s DNA, it may be possible to determine whether brothers and sisters are carriers of, or are affected by MPS I. There is a more detailed explanation of this complex subject in the booklet on inheritance available from the MPS Society.
For available treatment options and the latest news and information on research, therapies and clinical trials please visit our treatment section.