Hurler syndrome Health Article

Definition

Hurler syndrome is a rare, inherited disease of metabolism in which a person cannot break down long chains of sugar molecules called glycosaminoglycans (formerly called mucopolysaccharides).

Hurler syndrome belongs to a group of diseases called mucopolysaccharidoses, or MPS.

See also:

• MPS II Hunter syndrome
• MPS IV (Morquio syndrome
• MPS III (Sanfilippo syndrome
• MPS I S (Scheie syndrome

Alternative Names

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

Causes, incidence, and risk factors

Persons with Hurler syndrome do not make a substance called lysosomal alpha-L-iduronidase. This substance, called an enzyme, helps break down long chains of sugar molecules called glycosaminoglycans (formerly called mucopolysaccharides). 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. Both parents need to pass down the faulty gene in order for you to develop Hurler syndrome.

Hurler syndrome is a type of mucopolysaccharidosis called MPS I. Hurler syndrome 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

Symptoms of Hurler syndrome most often appear between ages 3 and 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:

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

Signs and tests

Urine tests are usually done first. These tests may show extra mucopolysaccharides, but they can't determine the specific form of MPS. More specific tests are done to diagnose the disease, including genetic testing for the alpha-L-iduronidase (IDUA) gene.

Other tests may include a spinal x-ray and EKG.