CFTR variants have been classified into five categories according to their clinical consequence: CF-causing variants, which are responsible for CF when combined in trans with a known CF-causing variant; CFTR-RD-causing variants, which are observed in patients with a CFTR-RD when combined in trans with a CF-causing variant; variants of varying clinical consequences (VVCC), which are reported as well in CF patients as in patients with a CFTR-RD when in trans with a CF-causing variant; variants of unproven or uncertain clinical significance (VUS) and variants with no clinical consequences [12]. Here, CFTR is linked to cystic fibrosis.