Hurler syndrome

Alternative Names

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

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.

Causes

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)

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:

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

Exams and Tests

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

Treatment

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

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

Other treatments depend on the organs that are affected.

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

Outlook (Prognosis)

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

When to Contact a Medical Professional

Call your health care provider if:

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

Prevention

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

References

Staba SL, Escolar ML, Poe M, et al. Cord-blood transplants from unrelated donors in patients with Hurler's syndrome. N Engl J Med. 2004 May 6;350(19):1960-9.

National Institute of Neurological Disorders and Stroke. Mucolipidoses Fact Sheet. Office of Communications and Public Liaison. Bethesda, MD; Publication No. 03-5115. February 13, 2007.

Wraith JE. Mucopolysaccharidoses and oligosaccharidoses. In: Saudubray JM, van den Berghe G, Walter JH, eds. Inborn Metabolic Diseases: Diagnosis and Treatment. 5th ed. New York, NY: Springer; 2012:chap 40.