CFTR and cystic fibrosis: During Sanger sequencing of the entire CFTR gene, the child was identified with the genotype F508del/[E217G;G509D],which includes the complex allele [E217G;G509D], which consists of the genetic variant G509D (c.1526G>A, p.Gly509Asp) and polymorphic variant E217G (c.650A>G, p.Glu217Gly), which according to the literature is considered as benign, not leading to cystic fibrosis (Figure 1).