A few individuals harbored variants that are known to recurrently arise de novo and also segregate in families with autosomal dominant diseases as exemplified by six cases with the common c.694dup, p.(Arg217Profs*8) pathogenic variant in the PRRT2 gene causing seizures and two individuals with multiple exostoses, carrying variants affecting the coding nucleotide 1018 in EXT1 (c.1018C>T, p.(Arg340Cys) and c.1018C>G, p.(Arg340Gly) respectively). The gene discussed is EXT1; the disease is autosomal dominant disease.