Study may lead to personalized treatments for cystic fibrosis Some 2,103 mutations have been identified in patients with cystic fibrosis (CF), the most common fatal genetic disease in Canada, and together they pose huge challenges for patients and researchers, including those affiliated with Université de Montreal and its teaching hospital, the Centre hospitalier de l'Université de Montréal (CHUM). Nearly 4,400 Canadians are today living with CF, which is caused by mutations in a gene called CFTR (cystic fibrosis transmembrane conductance regulator). Although the disease affects several organs, the main cause of death is related to the gradual deterioration of the lungs and their loss of function.