CFTR and cystic fibrosis: For instance, the majority of cystic fibrosis (OMIM 219700) cases in Caucasians (72%) are explained by CFTR p.Phe508del, whereas the presumptive founder mutation p.Trp1282Ter was the most prevalent variant in Ashkenazim explaining 46% of cystic fibrosis cases (compared to 1.5% in Europeans)7.