Two cystic fibrosis patients with the genotype G542X/G551D

Two adult sisters affected by cystic fibrosis were both shown to carry two different alterations within exon 11 of the CFTR gene, the nonsense mutation G542X and the missense mutation G551D. Both patients exhibit a relatively benign clinical course. In the described patients, G542X functions as a "mild" allele and is, in this respect, dominant to the "severe" G551D.