Sequencing was performed as described elsewhere12 16 19 and confirmed the most common molecular cause of HHT was a heterozygous loss-of-function variant in ENG or ACVRL1: Clinical Genomic Medicine Service reports indicated 65 of the recruited families had heterozygous, rare variants in either ENG (HHT1, N=35) or ACVRL1 (HHT2, N=30). This evidence concerns the gene ACVRL1 and hereditary hemorrhagic telangiectasia.