MPS I

MPS I (Hurler, Hurler-Scheie, Scheie syndrome)

MPS I, along with six other MPS diseases is a mucopolysaccharide disease that is relentlessly progressive and potentially fatal. MPS I has also been called Hurler, Hurler-Scheie and Scheie syndrome . Hurler takes its name from Gertrude Hurler, the doctor who described a boy and girl with the condition in 1919. In 1962, Dr. Scheie, a consultant ophthalmologist, wrote about some of his patients who were more mildly affected. Individuals who seem not to fit clearly in either the severe or the mild end of the disease were said to have Hurler/Scheie. The specific disease names have been replaced with the designations attenuated (diminished severity) and severe MPS I. There is no cure for MPS diseases, but 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. Children with these diseases 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.

Which disease does my child have?

MPS I (Hurler-Scheie) is a continuum of severity based upon the symptoms, ranging from severe to attenuated. There is a great deal of variability of symptoms among individuals with MPS I, often making the specific designation difficult. Generally, severe MPS I will present within the first year of life while less severe (attenuated) forms present during childhood. Although individuals with attenuated MPS I have normal intelligence, they may have a variety of symptoms that can range from mild to severe.

How common are these diseases?

It has been estimated that in British Columbia, 1 in 100,000 babies born would have Hurler. The estimate for Scheie is 1 in 500,000, births and for Hurler/Scheie it is 1 in 115,000. There is an estimate in the United States that 1 in 25,000 births will result in some form of MPS.

How is the disease inherited?

We all have genes inherited from our parents which control whether we are tall, short, fair, etc. Some genes we inherit are “recessive,” that is to say we carry the gene, but it does not have any affect on our development. MPS I (Hurler-Scheie syndrome ) is caused by a recessive gene. If an adult carrying the abnormal gene marries another carrier, there will be a one in four chance with every pregnancy that the child will inherit the defective gene from each parent and will be affected with the disease. There is a two in three chance that unaffected brothers and sisters of children with MPS I will be carriers. They can be reassured; however, that, as the disease is so rare, the chance of marrying another carrier is very slight provided they do not marry a cousin or other close family member.

Is there cure for MPS I?

There is no cure but treatments such as bone marrow transplantation and/or enzyme replacement therapy (ERT) can help make MPS I a more manageable disease. On April 30, 2003, the U.S. Food and Drug Administration (FDA) granted marketing approval for the orphan drug Aldurazyme (laronidase). Aldurazyme is the first and only FDA approved ERT treatment developed through recombinant DNA technology for individuals with MPS I. For more information, visit the treatment website at http://www.aldurazyme.com.

All families of affected children should seek further information from their doctor or from a Genetic Counselor.