Phenotypic discordance in three siblings affected by atypical cystic fibrosis with the F508del/D614G genotype.

We report an example of atypical CF, i.e., a family in which three siblings were affected by late-diagnosed mild CF, and showed discordant pulmonary and pancreatic phenotypes. Sibling no. 1 (male), showed a severe pulmonary involvement and pancreatic sufficiency; sibling no. 2 (female) showed a mild pulmonary disease with pancreatic sufficiency; sibling no. 3 (male) had a very mild pulmonary expression and pancreatic insufficiency. The sweat test was altered in all three siblings, and all had intestinal occlusion in young age. The whole scanning of CFTR revealed the rare F508del/D614G genotype. The discordance of clinical expression within the same family reinforces the putative role of modifier genes of CF phenotype.