The c.170T>G (p.Phe57Cys) variant in MAP2K2 has been reported in the literature as an unconfirmed de novo occurrence in a patient with clinical features of a RASopathy (PM6; PMID 16439621). In vitro functional studies provide some evidence that the p.Phe57Cys variant may impact protein function (PS3; PMID 16439621). This variant was absent from large population studies (PM2; ExAC, http://exac.broadinstitute.org). A different pathogenic missense variant has been previously identified at this codon of MAP2K2 (p.Phe57Val for malignant melanoma) which may indicate that this residue is critical to the function of the protein (PM5; ClinVar 8273). The variant is located in the MAP2K2 gene, which has been defined by the ClinGen RASopathy Expert Panel as a gene with a low rate of benign missense variants and pathogenic missense variants are common (PP2; PMID 29493581). Furthermore, the variant is in a location that has been defined by the ClinGen RASopathy Expert Panel to be a mutational hotspot or domain of MAP2K2 (PM1; PMID 29493581). Computational prediction tools and conservation analysis suggest that the p.Phe57Cys variant may impact the protein (PP3). In summary, this variant meets criteria to be classified as pathogenic for RASopathies in an autosomal dominant manner. Rasopathy-specific ACMG/AMP criteria applied (PMID:29493581): PM6, PS3, PM2, PM5, PP2, PM1, PP3.