Mucopolysaccharidosis type I, or MPS I, is a rare, inherited condition in which the body cannot break down certain large sugar molecules called glycosaminoglycans. These molecules build up inside cells and can affect many organs over time. Newborn screening helps identify affected children early, when treatment can do the most good.
What causes MPS I
MPS I is caused by variants in the IDUA gene, which provides instructions for an enzyme called alpha-L-iduronidase. Without enough of this enzyme, sugar molecules accumulate in the lysosomes of cells, so MPS I is a lysosomal storage disorder. It is inherited in an autosomal recessive pattern and ranges from a severe early form (often called Hurler syndrome) to milder, later-onset forms.
How newborn screening detects it
Newborn screening measures alpha-L-iduronidase enzyme activity in the blood spot from the heel prick. A low result prompts confirmatory enzyme testing and IDUA gene analysis to clarify the diagnosis and severity.
How MPS I is treated
Treatment depends on the form and its severity. Enzyme replacement therapy supplies the missing enzyme through infusions, and for severe early-onset MPS I a hematopoietic stem cell transplant may be recommended. Earlier treatment generally leads to better outcomes, which is why prompt diagnosis matters.
How genetic screening fits in
State newborn screening does an excellent job of catching MPS I. Genetic screening looks at the same picture from the DNA level and, in a single test, can also assess the genes tied to more than 1,000 other clinically actionable childhood conditions, many of which are not on any state panel. Fore Genomics offers an at-home cheek-swab screen, sequenced in CLIA-certified and CAP-accredited labs, with results supported by board-certified genetic counselors. See what we screen for or start screening.
Frequently asked questions
Is MPS I on newborn screening panels?
Yes. MPS I is on the federal Recommended Uniform Screening Panel and is screened for by a growing number of states.
Why does early treatment matter?
Starting enzyme replacement therapy or transplant early, before damage accumulates, generally leads to better long-term outcomes.
Is it inherited?
Yes. MPS I is autosomal recessive, so a child inherits an IDUA variant from each parent.
Related guides
- Newborn Screening Guide (all conditions and states)
- Pompe Disease
- SCID (Severe Combined Immunodeficiency)
Medically reviewed by Fore's Clinical Team. This article is for general educational purposes and is not medical advice. Sources: HRSA Newborn Screening; National Organization for Rare Disorders (NORD).