What causes cystic fibrosis?

Cystic fibrosis is a genetic recessive disease caused by mutations in the CFTR (cystic fibrosis transmembrane conductance regulator) gene. Mutations in CFTR lead to difficulty with electrolyte movement across the cell membranes of the cells that line our mucosal surfaces.^[1] CFTR is primarily expressed in the lungs, but is also expressed in the pancreas, sweat glands, intestine, liver, nasal passages, salivary glands, and reproductive tract.^[2] Up to 70% of patients with cystic fibrosis have a specific mutation involving a deletion of phenylalanine at codon 508. There are over 1600 possible (known) mutations of the CFTR gene, which exert a variety of effects, some of which result in milder forms of this disease. Excess pathogenic exposure leaves the respiratory system in a state of chronic, excessive inflammation, which causes irreversible damage, especially to the airway and lungs.^[3][2] Staphylococcus aureus is still the pathogen most frequently found in the lungs of children and adolescents with cystic fibrosis, with some estimates suggesting its occurrence at around 80% of people with the condition.^[2]