Since individuals with CS with other HRAS mutations, c.35G>T, c.35_36GC>TT and c.35_36GC>TA encoding the p.Gly12Val mutant protein have suffered from a very severe CS phenotype, we investigated the effect of these mutations on HRAS exon 2 splicing using a HRAS minigene. The gene discussed is HRAS; the disease is Cowden syndrome 1.