Although not an IEI, CFTR-related cystic fibrosis provides a phenotypically-relevant example where CFTR carriers have been shown in multiple studies to be at increased risk of cystic fibrosis-associated phenotypes including asthma, aspergillosis, and bronchiectasis (Çolak et al., 2020; Miller et al., 2020; Barton et al., 2022). This evidence concerns the gene CFTR and cystic fibrosis.