CFTR and cystic fibrosis: To date, more than 2,100 variants of the CFTR gene have been identified (Cystic Fibrosis Mutation Database, 2011), the distribution and frequency of which vary in different regions and ethnic groups (Bobadilla et al., 2002; Lao et al., 2003; Schrijver, 2011; World Health Organization [WHO], 2021].