The NM_000203.5:c.456G>A p.(Trp152Ter) variant in IDUA is a nonsense variant predicted to cause a premature stop codon in biologically-relevant-exon 4 out of 14, leading to nonsense mediated decay in a gene in which loss-of-function is an established disease mechanism (PVS1). This variant has been detected in at least one individual with MPS I. This individual is compound heterozygous for this variant and c.1513C>G p.(Arg505Gly), which has been classified as pathogenic or likely pathogenic by the ClinGen Lysosomal Diseases VCEP (PMID 31194252; phase unconfirmed; 0.25 points) (PM3 unmet). This variant is absent in gnomAD v4.1.0. (PM2_Supporting). The classification of this variant has been upgraded from Variant of Uncertain Significance to Likely Pathogenic based on the recommendations of the ClinGen Sequence Variant Interpretation Working Group, that a variant meeting PVS1 and PM2_Supporting is classified as Likely Pathogenic (https://clinicalgenome.org/site/assets/files/5182/pm2_-_svi_recommendation_-_approved_sept2020.pdf ). In summary, this variant meets the criteria to be classified as likely pathogenic for MPS I based on the IDUA-specific ACMG/AMP criteria applied, as specified by the ClinGen Lysosomal Diseases Variant Curation Expert Panel (Specifications Version 1.2.0): PVS1, PM2_supporting (Classification approved by the ClinGen Lysosomal Diseases Variant Curation Expert Panel on May 4, 2026)