Two of our patients bearing the in cis co-segregated combination of p.Cys1400Ter with c.489+3A>G displayed a compound heterozygosity with the Poly-T tract and the TG tract 5T:TG12 and developed CFTR-RD and chronic lung disease with ascending age, characterised by reduced lung function, bronchiectasis and equivocal sweat test results. Here, CFTR is linked to chronic lung disease.