As a first step toward establishing the endogenous disaccharide method [10] in our laboratory, we measured the MPS-I marker UA-HNAc(1S) as its PMP derivative in urine samples from all types of MPS patients (MPS-I, -II, -IIIA, -IIIB, -IIIC, -IIID, -IVA, -IVB, -VI, and VII) and found relatively high levels only in MPS-I urine (Table S3, consistent with the previous report [10]). Here, IDUA is linked to mucopolysaccharidosis.