The NM_000203.5:c.1139A>G variant in IDUA is a missense variant predicted to cause substitution of glutamine by arginine at amino acid 380 (p.Gln380Arg). This variant has been detected in at least 34 individuals with MPS I. Of those individuals, 20 were compound heterozygous for the variant and another variant in IDUA that has been classified as pathogenic or likely pathogenic variant for MPS I by the ClinGen LD VCEP, all in unknown phase. The second variant includes c.46_57del (p.Ser16_Ala19del) (PMID: 35141277) (0.5 pt), c.208C>T (p.Gln70Ter)(11 patients, PMID: 24368159, 24875751, 35141277) (max 2 x 0.5 points), c.979G>C p.Ala327Pro (PMID: 28752568) (0.5 pt), c.1205G>A p.Trp402Ter (6 patients, PMID: 28752568, 35141277) (max 2 x 0.5 pts), c.1861C>T (p.Arg621Ter) ((PMID: 11735025) (0.25 pt). Four unrelated individuals are homozygous for the variant PMID: 19396826, 31194252, 35141277) (max 2 x 0.5 pts). Total 4.25 points (PM3_VeryStrong). At least 19 patients with this variant had documented IDUA deficiency within the affected range in leukocytes, and/or urinary GAGs expressed as either total GAGs and/or specific GAG elevation above normal range, and/or clinical features specific to MPS I including dysostosis multiplex, corneal clouding, and hepatosplenomegaly (PP4_Moderate). The highest population minor allele frequency in gnomAD v4.10. is 0.00003112 (36/1156956 alleles) in the NFE population (gnomAD v2.1.1 is 0.00004458 with 3/67302 alleles in the NFE population), which is lower than the ClinGen Lysosomal Diseases VCEP’s threshold for PM2_Supporting (<0.00025), meeting this criterion (PM2_Supporting). The computational predictor REVEL gives a score of 0.872 which is above the threshold of 0.773, evidence that correlates with impact to IDUA function at the moderate level based on the specifications of the ClinGen Lysosomal Diseases VCEP (PMID: 36413997) (PP3_Moderate). There is a ClinVar entry for this variant (Variation ID: 550799). In summary, this variant meets the criteria to be classified as 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 1.0.0): PM3_Very Strong, PP3_Moderate, PP4_Moderate, PM2_Supporting. (Classification approved by the ClinGen Lysosomal Diseases Variant Curation Expert Panel on December 6, 2024)