CF results from biallelic pathogenic variants in the CFTR gene, which encodes the cystic fibrosis transmembrane conductance regulator—a chloride channel expressed in epithelial cells throughout the body. CFTR dysfunction impairs chloride transport, secondarily affecting sodium and water transport and resulting in thickened, abnormally viscous secretions across affected epithelia. The condition follows autosomal recessive inheritance, requiring two pathogenic CFTR alleles for disease expression. Per GeneReviews genotype-phenotype correlations documented on the Clinical and Functional Translation of CFTR (CFTR2) website, the strongest correlations have been identified in relation to pancreatic function. Two copies of variants causing severe CFTR dysfunction are associated with pancreatic insufficiency and markedly elevated sweat chloride. Respiratory phenotype shows broader variation that is less directly predicted by genotype. CFTR pathogenic variant classes—spanning protein absence (classes I–II) to reduced function (classes III–IV)—have direct implications for eligibility and responsiveness to CFTR modulator therapies.

Diagnostic criteria for CF are well established per GeneReviews. The diagnosis is confirmed by an elevated sweat chloride of 60 mmol/L or above on two separate tests, combined with clinical features consistent with CF or a positive newborn screening result. Newborn screening programs for CF are widely implemented in the United States and many other countries. Molecular genetic testing of CFTR confirms the diagnosis and characterizes specific pathogenic variants, which is relevant to eligibility for CFTR modulator therapies. The differential diagnosis includes other causes of chronic lung disease, pancreatic insufficiency, and male infertility, including primary ciliary dyskinesia and Shwachman-Diamond syndrome, per GeneReviews. Sweat testing remains the primary biochemical diagnostic test. Carrier testing and prenatal diagnosis are available for families in whom pathogenic variants have been identified.

A broad range of FDA-approved therapies is documented for CF. Foundational supportive therapies include airway clearance techniques (chest physiotherapy, vest therapy), pancreatic enzyme replacement therapy with meals and snacks, nutritional supplementation including fat-soluble vitamins, and inhaled mucolytics including dornase alfa (Pulmozyme, approved 1993) to reduce mucus viscosity and improve airway clearance. Inhaled antibiotics for chronic Pseudomonas aeruginosa colonization include tobramycin—available as TOBI (approved 1997), Tobramycin Inhalation, TOBI Podhaler, and Tobramycin Inhalation Solution Pak—and aztreonam inhalation (Cayston, approved 2010). Inhaled mannitol (Bronchitol, approved 2020) is documented as an approved osmotic agent for airway hydration. CFTR modulator therapies addressing the underlying protein defect include ivacaftor (Kalydeco, approved 2015), a CFTR potentiator; lumacaftor/ivacaftor (Orkambi, expanded 2018); tezacaftor/ivacaftor (Symdeko, approved 2018); elexacaftor/tezacaftor/ivacaftor (Trikafta, expanded approval 2023); and vanzacaftor/tezacaftor/deutivacaftor (Alyftrek, approved December 2024). Per GeneReviews, CFTR modulators are classified as targeted therapies addressing the underlying mechanism of disease causation, with eligibility depending on the specific CFTR genotype. Environmental smoke, exposure to respiratory infections, and dehydration are documented in GeneReviews as circumstances warranting avoidance.

The natural history of CF has been substantially modified by advances in CFTR-targeted therapy. Per GeneReviews, more than 50% of CF-affected individuals in the United States are now older than 18 years, reflecting improved survival compared to prior decades. Pulmonary disease remains the primary driver of morbidity and the leading cause of mortality. Bronchiectasis progresses over time in the absence of effective management. CFTR modulator therapies, particularly triple-combination regimens in eligible genotypes, have demonstrated clinically meaningful improvements in FEV1 and other pulmonary outcomes per GeneReviews treatment documentation. Nutritional status is closely linked to pulmonary outcomes in longitudinal data. Extrapulmonary complications—including CF-related diabetes, hepatic disease, and bone disease—may develop over time and contribute to overall health trajectory. GeneReviews notes that therapeutic interventions for CF are continually evolving, with research directed toward expanding modulator accessibility and developing mRNA-based and gene-based approaches.

Numerous active clinical trials for CF are registered on ClinicalTrials.gov. Documented active studies include natural history research in noncirrhotic portal hypertension in CF, long-term efficacy and safety evaluation of elexacaftor/tezacaftor/ivacaftor, bioavailability studies of VX-581 tablet formulations, the role of genetic factors in lung disease development, sinus disease in young children with CF, and impact of sinus surgery on affected individuals. Phase 1/2 investigation of VX-522 in CF participants is documented as an active study. Per GeneReviews, therapeutic interventions for CF are continually evolving, with ongoing research tracked by the Cystic Fibrosis Foundation. Research directions include next-generation CFTR modulator combinations, mRNA therapies encoding functional CFTR protein, and gene-based approaches targeting CFTR restoration across a broader range of genotypes.