Mucopolysaccharidosis Type I (MPS I) is a genetic condition where the body lacks an enzyme called alpha-L-iduronidase which is crucial for breaking down sugar molecules in the body.
Without it, these molecules build up, causing various health problems. There are two forms of MPS I: a severe type and a milder form. Children with severe MPS I seem normal at birth but may show symptoms before turning one. They might develop organ bulging, facial coarseness, spine issues, frequent infections, and delays in development. By age three, growth slows, and hearing loss is common. Enlarged liver and spleen, heart and lung disease, and fluid accumulation around the brain can occur. Lifespan is usually shortened, but treatment can extend it. Attenuated MPS (also known as Hurler-Scheie or Scheie syndrome), this form appears between ages 3 and 10. Severity varies, with some leading normal lives and others facing complications. Joint disease, heart and lung problems, learning disabilities, and hearing loss are common. Treatment involves immature cell use and bone-marrow transplants, but outcomes vary. Cord blood transplant is another option, and enzyme replacement therapy can alleviate symptoms.
MPS I is caused by pathogenic (disease-causing) variants in the IDUA gene and exhibits autosomal recessive inheritance. This means that both parents must be carriers to have a 25% chance to have a child with the condition. The risk of being a carrier is based on a person’s ancestry or ethnic background.
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Revised November 2023
