• Overview
• Inheritance
• Symptoms
  • Growth, Bones and Joints
  • Brain and Nerves
  • Physical Appearance
  • Ear, Nose, Throat and Chest
  • Heart
  • Liver, Spleen and Abdomen
  • Eyes
• Testing
• Treatment
• Resources

Hurler syndrome (pronounced "her-ler") affects about 1 in 100,000 people of all ethnic backgrounds. Hurler syndrome is caused by an absence or shortage of the enzyme alpha-L-iduronidase ("al-fuh L ih-der-on-eh-daze"), which normally breaks down long chains of sugar molecules, called glycosaminoglycans ("gly-kos-uh-mean-o-gly-cans") or GAGs. This chemical breakdown happens inside of the lysosomes of the body's cells. If the alpha-L-iduronidase enzyme is absent or in short supply, the GAGs cannot be broken down. Instead, GAGs build up in the lysosomes in the brain, heart, liver, spleen, bones, and other organs of the body; this build-up causes the symptoms of Hurler syndrome.

Symptoms include: short stature, mental retardation, characteristic facial features, breathing difficulties, heart disease, bone problems, and cloudiness to the cornea (the front covering of the eye). The symptoms of Hurler syndrome usually appear between 6 months and 2 years of age and may vary somewhat from person to person. Lifespan in people with Hurler syndrome is much shorter than normal. Only half of all affected people live past age 5, and most do not survive beyond age 10.

Common Symptoms:

• Short stature
• Mental retardation
• Characteristic facial features (e.g. short nose, flat face, large head)
• Corneal clouding
• Deafness
• Chronic runny nose
• Breathing difficulties and snoring
• Heart disease
• Enlarged liver and spleen
• Hernia
• Diarrhea/constipation
• Bone problems
• Joint stiffness

Hurler syndrome is one of a group of conditions called mucopolysaccharidoses (mu-ko-polly-sack-are-eye-doe-sees), or MPS. The other forms of MPS type I are called Hurler-Scheie ("her-ler shay") syndrome and Scheie ("shay") syndrome. There is a continuum of severity from Scheie syndrome to Hurler syndrome, with Hurler-Scheie syndrome being of intermediate severity. All three forms of MPS type I are caused by an absence or shortage of the enzyme alpha-L-iduronidase, and all three cause similar symptoms. However, Hurler syndrome, Hurler-Scheie syndrome, and Scheie syndrome differ in the age of onset of symptoms, the severity of symptoms, and the lifespan of affected individuals. Hurler syndrome is the most severe form of MPS type I.