Alternative Names: Alpha-L-iduronate deficiency; Mucopolysaccharidosis type I; MPS I; Hurler-Scheie Syndrome (MPS 1 H/S); Scheie Syndrome (MPS1S)

Causes, incidence, and risk factors:

Hurler syndrome (MPS1) is an inherited and progressive disorder that results from the body's inability to make�lysosomal alpha-L-iduronate, an enzyme�that�helps breakdown mucopolysaccharides.�Mucopolysaccharides are made of a Jello-like material and are found throughout the body, often in mucus secretions and in fluids surrounding the joints.

The enzyme deficiency found in Hurler syndrome causes mucopolysaccharides�to build up in the body.� The result is a multisystem disorder with symptoms that range from mild to severe. The disease damages many organs, including the heart.

In the past, MPS1 was called Hurler syndrome, Hurler-Scheie syndrome, or Scheie syndrome. Because there is no clear distinction between the groups,�a�classification based on disease severity has been suggested:

• Hurler as severe MPS1
• Hurler-Scheie as intermediate MPS1
• Scheie as mild MPS1

Hurler syndrome is inherited as an autosommal recessive trait.�Approximately 1 in 115,000 individuals are affected.

Symptoms:

The symptoms of intermediate MPS1 usually develop�between 3 and 8 years of age. Survival into adult life is common.

Infants with severe MPS1 appear normal at birth. Coarsening of facial features is noted during the first two years of life. Symptoms are progressive and include:

• Halted growth
• Progressive� mental retardation
• Thick, coarse facial features with low nasal bridge
• Cloudy corneas
• Deafness
• Joint disease, including stiffness
• Heart value problems
• Abnormal bones of spine and claw hand

Signs and tests:

Tests that may be performed include:��

• Urine testing for mucoploysacchariduria (heparan and dermatan sulphate). Urine studies are usually conducted first. They may�show excess MPS when present, but can not determine the exact form of MPS. A definite diagnosis�relies on specific enzyme testing.�
• Alpha-L-Iduronidase testing in blood, skin or plasma
• Molecular genetic testing for the Alpha-L-Iduronidatase (IDUA) gene
• Spine�x-ray
• EKG�

Treatment:

Enzyme replacement therapy is now possible for patients with a defect in the enzyme a-L-iduronidase.

Bone marrow transplantation can improve some of the symptoms of the disease. To prevent mental retardation, a bone marrow transplant probably should be performed at a very young age. Other treatments depend on the affected organ system.

Support Groups:

For more information and support, contact one of the following organizations:

• The National MPS Society: www.mpssociety.org
• Canadian Society for MPS and Related Diseases: www.mpssociety.ca
• Society for MPS Diseases: www.mpssociety.co.uk

Expectations (prognosis):

Hurler syndrome is a disease with a poor prognosis. Children with this disease have progressive neurological impairment. Early death can occur.