The NM_000277.3:c.198A>G variant in PAH is a synonymous (silent) variant (p.Glu66=) that is not predicted to impact splicing. To our knowledge, this variant has not been reported in the literature and results of functional studies are unavailable. The highest population minor allele frequency in gnomAD v2.1.1 is 0.00002641 (3/113600 alleles) in the European (non-Finnish) population, which is lower than the ClinGen PAH VCEP’s threshold for PM2_Supporting (<0.0002), meeting this criterion (PM2_Supporting).There is a ClinVar entry for this variant (Variation ID: 760907, 1 star review status) with one submitter classifying the variant as a variant of uncertain significance and one submitter classifying the variant as likely benign. In summary, this variant meets the criteria to be classified as a variant of uncertain significance for PAH deficiency based on the ACMG/AMP criteria applied, as specified by the ClinGen PAH Variant Curation Expert Panel (Specifications Version 2.0): PM2_Supporting.