The c.548A>T (p.Glu183Val) variant in PPP1CB is a missense variant predicted to cause substitution of glutamate by valine at amino acid 183. This variant is absent from gnomAD v2 (PM2_Supporting). PPP1CB, in which the variant was identified, is defined by the ClinGen RASopathy VCEP as a gene that has a low rate of benign missense variation and where pathogenic missense variants are a common mechanism of disease. The missense Z-score is 4.33 which is above the threshold set by the Rasopathy VCEP (PP2). This variant was observed in a proband with a phenotype consistent with RASopathy (PS4_Supporting; PMID:27681385). This variant has also been identified as a de novo occurrence with confirmed parental relationships in 1 individual with features of RASopathy (PS2; PMID:27681385). The variant occurs at the same amino acid residue as the PPP1CB c.548A>C (p.Glu183Ala) variant, which has been classified as pathogenic by the ClinGen RASOpathy VCEP (PM5). Based on ACMG/AMP criteria, this variant has enough supporting evidence to be classified as likely pathogenic; however, the RASopathy VCEP has upgraded this classification to pathogenic based on ClinGen policy due to the strength of evidence for the PM5 code. In summary, this variant currently meets the criteria to be classified as pathogenic for autosomal dominant RASopathy based on the ACMG/AMP criteria applied, as specified by the ClinGen RASopathy VCEP: PS2, PM5, PP2, PS4_Supporting, PM2_Supporting. (RASopathy VCEP specifications version 1.3; 12/3/2024)