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Alpha-L-iduronidase is encoded by the IDUA gene. Pathogenic mutations to IDUA gene lead to a defective alpha-L-iduronidase enzyme with lesser than normal enzyme activity.1 A definitive diagnosis is established by:

  • α-L-iduronidase enzyme activity assay: demonstrating absence or deficiency (does not allow for differentiation between severe and attenuated)1
  • IDUA gene sequencing: demonstrating two pathogenic variants in trans (one from each parent). Though identification of mutant alleles may not be required for diagnosis, sequencing the IDUA gene can provide secondary confirmation after enzymatic testing and can provide important information related to phenotype1


This is not an exhaustive list of labs, or an endorsement of any one lab. Other testing options can be found at (free login required) or Sanofi Genzyme does not review or control the content of non-Sanofi Genzyme websites. These listings do not constitute an endorsement by Sanofi Genzyme of information provided by any other organizations. Tests may not be available in all states. Please contact the laboratory to confirm test availability, sample shipping information, and all other logistics.

MPS I Diagnostic Delay

Patients typically are referred to several specialists before they are correctly diagnosed. Misdiagnoses and diagnostic delays are common, especially in attenuated MPS I.


mps i gap onset diagnosis


Recommended Minumum Evaluation Schedule



1. Clarke LA. NCBI Bookshelf, a service of the National Library of Medicine, National Institutes of Health (NIH). Available at: Accessed July 20, 2018.








Last Updated: Feb 6, 2021
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