March 2026 Research Update

This month, research on newborn screening suggests that adding a second blood-spot test can change what kinds of MPS I cases programs end up identifying after an initial screen. Across US programs, those that used a second-tier test measuring glycosaminoglycans (GAGs, sugars that build up in MPS I) reported a higher proportion of severe MPS I among confirmed cases, while the share of attenuated cases looked similar. The same approach was also linked to a slightly lower proportion of pseudodeficiency results, which are screening findings that look abnormal but do not lead to disease. [1]

A tradeoff in these program-level results was that programs using second-tier GAG testing noted more cases with an undetermined phenotype at the time of reporting. In plain language, this means the second test may help sort out some false alarms, but it can also leave some families in a temporary "not sure yet" category until more follow-up information is available. The report also highlighted that uncertainty remains around how well newborn screening (with or without second-tier GAG testing) reliably captures the attenuated form early on. [1]

For families, this mainly adds context about why newborn screening results can look different depending on where a baby is born and what follow-up testing is built into the program. The findings may matter now for understanding screening pathways, but they do not by themselves prove that one approach is best for every state because the data describe how programs performed in routine practice rather than testing a single standardized method. What became clearer is that second-tier GAG testing may shift results toward finding more severe cases and slightly fewer pseudodeficiency outcomes, while leaving some children temporarily hard to classify. [1]

This month, a larger single-center patient review reinforced that carpal tunnel syndrome is very common in children with mucopolysaccharidosis type I (MPS I) and can start early in life. Most patients in the report were diagnosed with carpal tunnel syndrome, with onset around early childhood, and the risk appeared highest in the first years of life. The study also noted that symptoms can come back even after surgical release, meaning this can be an ongoing issue rather than a one-time event. [2]

The same report added a biological detail that helps explain why carpal tunnel problems may persist: several children had ongoing lysosomal storage material seen in tissue, even after hematopoietic stem cell transplantation (HSCT, a transplant that can treat MPS I). In plain language, this suggests that some hand and wrist tissues may still show storage changes despite systemic treatment, which could relate to continued nerve compression and recurrence after surgery. The study also described that carpal tunnel syndrome was diagnosed using tests like nerve testing or ultrasound, reflecting the need for objective checks when symptoms may be hard for young children to describe. [2]

For patients and caregivers, this evidence may matter now as an explanation of what families often face over time: carpal tunnel syndrome can appear early, may need monitoring with testing rather than symptoms alone, and may recur after a procedure. It also adds understanding that HSCT does not necessarily prevent all local storage changes in every tissue, which may help explain why some complications still occur. What remains uncertain from this single retrospective report is how often these patterns occur across different centers and care approaches, and which factors best predict recurrence in an individual child. [2]

This month included early research aiming to deliver the missing IDUA enzyme in new ways, plus a single case report describing an uncommon reproductive finding. In mice, two different approaches increased IDUA activity and reduced GAG storage in targeted areas, but these are still animal and laboratory results and do not tell us yet how well they would work in people. Separately, one patient report raised a question about whether MPS I could be linked to uterine development changes, but it could not show that MPS I caused the finding. [3] [4] [5]

One mouse study used lipid nanoparticles to deliver mRNA coding for human IDUA and included a peptide intended to help the treatment reach the brain. The researchers reported higher IDUA activity in blood and liver, lower GAGs in urine and tissues, and improvements in heart, bone, and a learning test, with reductions seen in some brain regions. This supports the idea that repeated dosing might address both body and parts of the central nervous system in an animal model, but the summary did not describe safety outcomes and it remains preclinical. [3]

A second preclinical study focused on joints by injecting a nonviral CRISPR/Cas9 gene-editing system directly into mouse knees to increase local IDUA production. The researchers observed higher IDUA activity in joint tissue and joint fluid and lower GAG levels, with no systemic IDUA detected, which points to a "local-only" approach aimed at joint disease. In laboratory joint-lining cells, IDUA activity lasted up to 30 days with low cytotoxicity, and the animal results included detectable editing in joint DNA. [4]

The case report described a 13-year-old with attenuated MPS I who had genetic confirmation of IDUA variants and very low enzyme activity, along with imaging showing a small, infantile-appearing uterus. The authors discussed possible explanations, such as effects of storage material on hormonal signaling or delayed puberty, but emphasized that no causal link is established from a single case. The report mainly signals an area where more systematic research would be needed to know whether reproductive organ differences are part of MPS I for some individuals. [5]

For families, these findings mostly matter as research direction rather than something that changes care now. The mouse studies help clarify what scientists are trying to solve next: getting treatment effects into hard-to-reach areas like the brain, and improving joint disease with local delivery, while tracking whether the effect stays local or becomes body-wide. What remains unknown is whether these approaches will be safe, durable, and effective in people, since no human results were reported. The single patient report may help families feel seen if reproductive development questions arise, but it is not enough to say this is a common or expected part of MPS I. [3] [4] [5]