PURPOSE: This study reports on the phenotype of cystic fibrosis patients 
identified to be carriers of the p.Ser489X (p.Ser489*; c.1466C>A) cystic 
fibrosis transmembrane conductance regulator (CFTR) mutation, a variant rarely 
described in the cystic fibrosis literature, as well as on its allelic frequency 
in a French-Canadian cystic fibrosis patient cohort.
METHODS: Reported phenotypes and allelic frequency of this variant were 
collected based on the data from a large French-Canadian cystic fibrosis patient 
cohort.
RESULTS: Cystic fibrosis patients found to carry the p.Ser489X variant generally 
presented with classic gastrointestinal manifestations of this condition in 
infancy. The allelic frequency of this variant was calculated to be 0.7% for 
this population.
CONCLUSION: The p.Ser489X CFTR variant is a severe disease-causing CFTR allele 
that is relatively frequent in the French-Canadian cystic fibrosis patient 
population, warranting its inclusion into CFTR molecular testing panel for this 
population.