The NM_001114753.3: c.991G>A variant in ENG is a missense variant predicted to cause substitution of glycine by serine at amino acid 331 (p.Gly331Ser). This variant is absent from gnomAD v2.1.1 (PM2_Supporting). This variant has been reported in >10 probands with a phenotype consistent with HHT (PS4; PMID: 19767588, 34872578, 16690726, 34880085, 15517393, 25970827, 29171923, 32573726, 21158752, Internal lab contributors). At least one patient's phenotype meets Curacao Criteria for HHT, and sequencing and large deletion/duplication analysis was performed for ENG and ACVRL1, which is highly specific for HHT (PP4_Moderate; PMID: 19767588, 21158752). The variant has been reported to segregate with HHT in 3 affected meioses from 2 families (PP1; PMID: 19767588, 34872578). The computational predictor REVEL gives a score of 0.202, which is neither above nor below the thresholds predicting a damaging or benign impact on ENG function. However, RT-PCR analysis of cDNA demonstrated that the variant impacts splicing by leading to exon 7 skipping (PS3; PMID: 16690726). In summary, this variant meets the criteria to be classified as pathogenic for autosomal dominant hereditary hemorrhagic telangiectasia based on the ACMG/AMP criteria applied, as specified by the ClinGen Hereditary Hemorrhagic Telangiectasia Variant Curation Expert Panel: PS3, PS4, PP4_Moderate, PP1, PM2_Supporting (specification version 1.0.0; 1/4/2024).