The c.149C>T (p.Thr50Ile) variant in NRAS is a missense variant predicted to cause substitution of threonine by isoleucine at amino acid 50. This variant is absent from gnomAD v2.1.1 (PM2_Supporting). The computational predictor REVEL gives a score of 0.693, which is neither above nor below the thresholds predicting a damaging or benign impact on NRAS function. This variant has been reported in over 6 probands with features of RASopathy (PS4; PMIDs: 22855653, 28594414, 31219622, GeneDx). This variant has been identified as a de novo occurrence with unconfirmed parental relationships in 4 individuals with autosomal dominant RASopathy (PM6_VeryStrong; PMIDs: 19966803, 29752777, APHP-Robert Debré). MEK and ERK activation assays in COS-7 cells showed enhanced phosphorylation of MEK and ERK in the presence of serum or after EGF stimulation indicating that this variant impacts protein function (PMID: 19966803)(PS3_Moderate). In summary, this variant 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: PM6_VeryStrong, PS4, PS3_Moderate, PM2_Supporting. (RASopathy VCEP specifications version 2.1; 9/17/2024)