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. If both parents carry the defective gene related to this condition, each of their children has a 25% chance of developing the disease.
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)