A Family Guide to Non-Oncologic Blood Disorders
Hurler Syndrome
What is Hurler syndrome? Hurler syndrome, also known as mucopolysaccharidosis I (MPS-I), is part of a subgroup of metabolic disorders known as MPS disorders. MPS disorders are caused by a mutation in a specific gene. Genes carry an inherited code of instructions on how to create every cell and substance in the body. The mutat- ed gene in MPS disorders affects an enzyme called alpha-L- iduronidase (IDUA). This enzyme is needed to break down long chains of sugar molecules called glycosaminoglycans (GAG). The body needs GAGs to build bones and tissues. MPS disor- ders allow GAGs to build up in the body and cause damage. What are some symptoms of Hurler syndrome? Hurler syndrome symptoms appear most often in ages 3–8 when GAGs build up in the body. Infants with severe Hurler syndrome can appear normal at birth and develop physical symptoms during the first 2 years of life. The following are the most common symptoms of Hurler syndrome. However, each child may experience symptoms differently. Symptoms may include: • Developmental disabilities • Heart problems • Hearing problems and frequent ear infections • Large head size, broad forehead, thick eyebrows, coarse facial features, low nasal bridge • Cloudy corneas • Halted growth • Deformed bones and stiff joints, including the spine, hips, knees, wrists, and fingers • Breathing problems and snoring How is Hurler syndrome diagnosed? A diagnosis of Hurler syndrome is usually made based on the following: • Complete medical his-
What tests or procedures will my child need? • Blood tests or skin samples to check if the body is pro- ducing the IDUA enzyme • Genetic tests for mutations to the gene for the IDUA enzyme • Urine tests that detect for extra GAGs • X-rays to check for damage in the spine or other joints and the widening of ribs • Electrocardiogram to check heart rhythm • Echocardiogram to measure the size and function of the heart What are the treatment options for Hurler syndrome? Stem cell transplant (SCT) is the only curative treatment option. The main goal in treating Hurler syndrome is to provide the body the missing enzyme so it can break down GAGs. Com- mon treatments include: • Immediate referral to a pediatric geneticist (a doctor who studies genes and their effects) • Enzyme replacement therapy, where your child is given a drug (laronidase) that has the IDUA enzyme his or her body is missing Your medical team will determine the best treatment plan for your child. How successful is the treatment? Enzyme replacement therapy can improve breathing, growth, and problems with the bones, joints, and heart. However, there is no evidence that it has any effect on mental develop- ment problems caused by Hurler syndrome. In order to stop damage caused by the disorder before it becomes severe, SCT has the best chance of success when it is performed soon after diagnosis. Children who receive a trans- plant early enough can have normal or near-normal mental development. Further damage to the organs is prevented and hearing may improve. However, transplants for children who have developed severe organ damage may not yield as favorable results. If there is already organ damage, the risk of developing life-threatening
• Physical examination • Specific blood tests or scans • Urine tests
tory, including history of infections and family history
Hurler Syndrome
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