Hurler syndrome

Alpha-L-iduronate deficiency; Mucopolysaccharidosis type I; MPS I H

People with Hurler syndrome do not make an enzyme called lysosomal alpha-L-iduronidase. This enzyme helps break down long chains of sugar molecules called glycosaminoglycans . These molecules are found throughout the body, often in mucus and in fluid around the joints.

Without the enzyme, glycosaminoglycans build up and damage organs, including the heart. Symptoms can range from mild to severe.

Hurler syndrome is inherited, which means that your parents must pass the disease on to you. If both parents carry a nonworking copy of the gene related to this condition, each of their children has a 25% (1 in 4) chance of developing the disease.

Hurler syndrome is a type of mucopolysaccharidosis called MPS I. It is the most severe type. It is categorized as MPS I H.

The other subtypes of MPS I are:

• MPS I H-S (Hurler-Scheie syndrome)
• MPS I S (Scheie syndrome)

Symptoms of Hurler syndrome most often appear between ages 3 to 8. Infants with severe Hurler syndrome appear normal at birth. Facial symptoms may become more noticeable during the first 2 years of life.

Symptoms include:

• Abnormal bones in the spine
• Claw hand
• Cloudy corneas
• Deafness
• Halted growth
• Heart valve problems
• Joint disease, including stiffness
• Intellectual disability that gets worse over time
• Thick, coarse facial features with low nasal bridge

These tests are done to check for Hurler syndrome:

• EKG
• Genetic testing for changes to the alpha-L-iduronidase (IDUA) gene
• Urine tests for extra mucopolysaccharides
• X-ray of the spine

Enzyme replacement therapy for Hurler syndrome adds a working form of the missing enzyme to the body. The medicine, called laronidase (Aldurazyme), is given through a vein (IV, intravenously). Talk to your health care provider for more information.

Bone marrow transplant has been used in several people with this condition. The treatment has had mixed results.

Other treatments depend on the organs that are affected.

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

Hurler syndrome is a disease with a poor outlook. Children with this disease develop nervous system problems, and can die young.

Call your provider if:

• You have a family history of Hurler syndrome and are considering having children
• Your child begins to show symptoms of Hurler syndrome

Experts recommend genetic counseling and testing for couples with a family history of Hurler syndrome who are considering having children. Prenatal testing is available.