Keywords: ACN, Acetonitrile; BAB, Butyl-4-aminobenzoate; CRIM, Cross Immune Reactive Material; ERT, Enzyme Replacement Therapy; GSD, Glycogen Storage Disease; GVUS, Genetic Variant of Unknown Significance; Glc4, Glcα1-6Glcα1-4Glcα1-4Glc, tetraglucose,; IOPD, Infantile-Onset Pompe disease; IS, Internal Standard; LOD, Limit of Detection; LOPD, Late-Onset Pompe disease; LOQ, Limit of Quantification; NaBH3CN, Sodium Cyanoborohydride; PD, Pompe Disease; QC, Quality Control; SPE, Solid Phase Extraction; del ex 18, c.2481+102_2646+31 del.