Cystic fibrosis is a common life-limiting autosomal recessive genetic disorder caused by mutations in the CFTR gene encoding the cystic fibrosis transmembrane conductance regulator, a chloride and bicarbonate channel expressed in epithelial cells. CFTR dysfunction leads to dehydrated, viscous secretions in multiple organ systems, most critically the airways and pancreas. Nearly 2,000 CFTR variants have been identified, with the Phe508del (F508del) mutation present in nearly 90% of patients. The disease is characterized by progressive bronchiectasis, chronic bacterial lung infection, exocrine pancreatic insufficiency, male infertility due to congenital bilateral absence of the vas deferens, and elevated sweat chloride. Multidisciplinary care and CFTR modulator therapies have extended median survival beyond 40 years, with the advent of elexacaftor-tezacaftor-ivacaftor (Trikafta) representing a transformational advance for the majority of patients.
Conditions with similar clinical presentations that must be differentiated from Cystic Fibrosis:
Cystic fibrosis (CF) is a monogenic autosomal recessive disorder caused by mutations in the CFTR gene, which encodes the cystic fibrosis transmembrane conductance regulator. The CFTR protein is an ATP-binding cassette (ABC) transporter-class ion channel that normally functions as a cAMP-regulated epithelial chloride channel (www.ncbi.nlm.nih.gov). It also regulates bicarbonate transport and influences other ion channels. In healthy epithelia, CFTR-mediated chloride and bicarbonate secretion balances sodium absorption to maintain hydration of mucosal surfaces (pmc.ncbi.nlm.nih.gov). In CF, CFTR dysfunction is the primary defect: mutations render the chloride/bicarbonate channel absent or defective at the cell surface (pmc.ncbi.nlm.nih.gov). As a result, epithelial ion transport is dysregulated – chloride and bicarbonate secretion is impaired while unchecked sodium absorption through the epithelial sodium channel (ENaC) leads to excessive water reabsorption (pmc.ncbi.nlm.nih.gov). The airway surface liquid becomes depleted and secretions thicken, causing viscous mucus that the cilia cannot clear (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). One review summarizes that in CF airways, “CFTR is diminished, and ENaC is upregulated, leading to mucus dehydration and increased chance of infection” (pmc.ncbi.nlm.nih.gov) (PMID: 23878362). This dehydrated, hyperviscous mucus is a hallmark of CF pathophysiology across multiple organs (pmc.ncbi.nlm.nih.gov). CFTR is expressed in the epithelial cells of the airways, submucosal glands, pancreas, intestines, biliary tract, sweat glands, and reproductive ducts, so CFTR dysfunction causes a complex multi-organ disease (www.nature.com). However, most morbidity and mortality in CF stems from the progressive lung disease resulting from mucus obstruction and its consequences (www.nature.com).
In the bronchopulmonary system, the loss of CFTR leads to abnormal ion and fluid transport on airway surfaces, producing thick, sticky mucus that clogs small airways (pmc.ncbi.nlm.nih.gov). Mucociliary clearance is impaired, and bacteria become trapped, leading to persistent airway infection. The lungs of CF patients often become colonized in early childhood with organisms like Staphylococcus aureus and Haemophilus influenzae, and later Pseudomonas aeruginosa and other gram-negative bacteria, resulting in chronic suppurative infection (news.unchealthcare.org) (news.unchealthcare.org). The stagnant mucus and microbes trigger a robust inflammatory response. Neutrophils are recruited excessively to CF airways (even in early life before overt infection) (respiratory-research.biomedcentral.com). These neutrophils release proteases and oxidants that cause tissue damage. Notably, neutrophil elastase (NE), a serine protease, is abundant in CF airway fluids and plays a central role in driving lung pathology (respiratory-research.biomedcentral.com). Studies have found high NE activity and IL-8 levels in bronchoalveolar lavage (BAL) fluid of infants with CF, correlating with the early development of bronchiectasis (respiratory-research.biomedcentral.com) (PMID: 29258516). NE and other proteases create a self-perpetuating cycle of inflammation: NE cleaves and inactivates important host defense molecules (like lactoferrin and complement components) (respiratory-research.biomedcentral.com), stimulates further chemokine release (IL-8) attracting more neutrophils (respiratory-research.biomedcentral.com), and directly impairs ciliary function while inducing goblet cell hyperplasia and mucin overproduction (respiratory-research.biomedcentral.com). As one review describes, “NE impairs ciliary beating and promotes expression of respiratory mucins (MUC5AC and MUC5B), resulting in muco-ciliary clearance failure.” (respiratory-research.biomedcentral.com). NE and other neutrophil proteases also degrade structural proteins (e.g. elastin in airway walls), leading to irreversible bronchiectasis (permanent airway dilation and remodeling) (respiratory-research.biomedcentral.com). Thus, CF lung disease is characterized by a vicious cycle of mucus obstruction → infection → neutrophilic inflammation → tissue damage, which perpetuates further obstruction and infection. Over years, this cycle causes progressive airway destruction, fibrosis, and loss of pulmonary function. The end-stage of CF lung disease is respiratory failure due to diffuse bronchiectasis and fibrotic lung changes.
Beyond the lungs, CFTR dysfunction affects other systems in parallel. In the pancreas, CFTR is crucial for bicarbonate and chloride secretion in pancreatic ducts. CFTR loss leads to thick, protein-rich secretions that obstruct the small pancreatic ducts (pmc.ncbi.nlm.nih.gov). This causes exocrine pancreatic insufficiency in ~85% of patients: digestive enzymes cannot reach the intestines, resulting in malabsorption of fats and protein, nutrient deficiencies, and steatorrhea (fatty stools) (pmc.ncbi.nlm.nih.gov). Pancreatic obstruction at birth can cause pancreatic damage (fibrosis) and explains why many CF infants have meconium ileus (intestinal blockage by thick meconium) shortly after birth. Recurrent obstruction and inflammation can also lead to pancreatitis in some CF individuals, and eventually CF-related diabetes (CFRD) due to islet cell destruction in later life (pmc.ncbi.nlm.nih.gov). In the intestines, thick secretions and abnormal ion/water transport lead to viscid meconium in neonates (meconium ileus, a neonatal intestinal obstruction pathognomonic for CF) and contribute to distal intestinal obstruction syndrome in older patients (pmc.ncbi.nlm.nih.gov). In the hepatobiliary system, thick bile and mucus can clog bile ducts, leading to focal biliary cirrhosis and gallstones; about 5–10% of CF patients develop multilobular cirrhosis or portal hypertension from bile duct obstruction and chronic inflammation in the liver. In the sinuses, CFTR mutations cause chronic rhinosinusitis and nasal polyps due to similar mucus stasis in sinus epithelia. Almost all CF patients have sinus radiographic abnormalities, and nasal polyps occur in ~10–20% (pmc.ncbi.nlm.nih.gov). The reproductive tract is also affected: >95% of males with CF have obstructive azoospermia due to congenital bilateral absence of the vas deferens (CBAVD), which results from CFTR’s role in embryonic development of the wolffian duct or early obstruction of the vas deferens (pmc.ncbi.nlm.nih.gov). Females with CF have generally normal anatomy but may have reduced fertility from thick cervical mucus and malnutrition. Finally, in the sweat glands, CFTR normally facilitates chloride (and sodium) reabsorption in sweat duct epithelia. CFTR loss renders sweat ducts unable to reclaim salt, leading to excessive salt loss in sweat – the classic “salty skin” of CF patients (pmc.ncbi.nlm.nih.gov). This was one of the earliest clues to CF’s nature: infants with CF were noted to taste salty, and in 1959 Gibson and Cooke introduced the pilocarpine sweat test as a diagnostic, which remains a standard test (sweat chloride ≥60 mM is strongly indicative of CF) (pmc.ncbi.nlm.nih.gov). Thus, the core pathophysiological feature of CF across organs is dehydrated, thick secretions due to defective epithelial ion transport, leading to obstruction, tissue damage, and dysfunction of affected organs.
Molecularly, thousands of different CFTR gene variants can cause CF, and these are grouped by their effect on the CFTR protein. Common mutations include F508del (deletion of phenylalanine at position 508), present on at least one allele in ~85–90% of CF patients worldwide (pmc.ncbi.nlm.nih.gov). The F508del mutation produces a misfolded CFTR protein that is tagged for degradation and fails to reach the cell surface (a Class II trafficking mutation) (pmc.ncbi.nlm.nih.gov). Other mutations produce no protein at all (Class I, nonsense or frameshift mutations), defective channel gating (Class III, e.g. G551D), decreased channel conductance (Class IV), reduced mRNA/protein production (Class V), or unstable surface expression (Class VI) (pmc.ncbi.nlm.nih.gov). Despite this genetic heterogeneity, the final common pathway is insufficient functional CFTR at the apical membrane of epithelial cells. The severity of ion transport dysfunction (and thus disease severity) can vary with mutation class and the amount of residual CFTR function (pmc.ncbi.nlm.nih.gov). For instance, “gating” mutations like G551D result in CFTR at the surface but non-functional, whereas milder mutations that allow some CFTR function may lead to atypical or less severe CF phenotypes (e.g. isolated CBAVD or pancreatic-sufficient CF). Environmental and modifier genes (involving inflammation, infection susceptibility, etc.) also contribute to the wide variability in disease severity among CF patients (www.nature.com) (www.nature.com).
Genes/Proteins: The key gene in CF is CFTR (HGNC:1884), located on chromosome 7q31.2, which encodes the CFTR protein (UniProt P13569). CFTR is a 1480-amino-acid glycoprotein that functions as a regulated chloride/bicarbonate channel in the apical membrane of epithelial cells (www.ncbi.nlm.nih.gov). CFTR’s activity is regulated by cAMP/PKA phosphorylation and ATP binding/hydrolysis at its nucleotide-binding domains. Mutations in CFTR (>2,000 variants identified) are causally responsible for CF (pmc.ncbi.nlm.nih.gov). The most prevalent pathogenic variant is F508del (p.Phe508del), which accounts for two defective alleles in ~44% of CF patients and one allele in another ~40% (pmc.ncbi.nlm.nih.gov). Other notable CFTR mutations include G551D (a gating defect), G542X (a premature stop codon), N1303K, W1282X, etc. All patients have biallelic CFTR mutations; the combination of mutations influences the phenotype (e.g. pancreatic-sufficient vs insufficient CF is often related to “milder” mutations that retain partial function (pmc.ncbi.nlm.nih.gov)). Aside from CFTR itself, no other single gene causes CF, but many modifier genes can modulate CF severity. For example, variants in genes encoding muco-inflammatory regulators (like MUC5B, TGFB1, TNF, EDNRA, etc.) and immune response genes (IL-8, MSRA) have been associated with differences in lung function or infection severity in CF (www.nature.com) (www.nature.com). These are not causal of CF, but they can exacerbate or ameliorate aspects of disease (so-called modifier gene effects). In the CF airways, ENaC (epithelial sodium channel) is a critical interacting protein (though not mutated in CF). ENaC is a heterotrimeric sodium channel (subunits α/β/γ encoded by SCNN1A, SCNN1B, SCNN1G) on the apical membrane of the same cells that express CFTR. CFTR normally downregulates ENaC activity; hence in CF, ENaC becomes overactive, driving increased Na⁺ absorption and airway surface liquid depletion (pmc.ncbi.nlm.nih.gov). This makes ENaC a key contributor to the airway surface dehydration in CF pathophysiology. As a result, ENaC is being explored as a therapeutic target (e.g. inhaled ENaC inhibitors) to complement CFTR modulator therapy (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). Other proteins involved in CF pathology include mucins like MUC5AC and MUC5B (the major gel-forming mucins in airway mucus). Their genes are not mutated in CF, but their expression and properties are altered secondary to CFTR dysfunction and chronic inflammation (respiratory-research.biomedcentral.com). In CF, mucins tend to be overly concentrated and improperly unfolded due to lack of bicarbonate; this contributes to the dense mucus plaques that obstruct airways (news.unchealthcare.org). Neutrophil elastase (ELANE gene) is another key protein in CF lung disease: it is a protease released by neutrophils that damages tissues and mucus clearance mechanisms, as discussed above. Elevated elastase activity is a biomarker of CF airway disease severity (respiratory-research.biomedcentral.com) (respiratory-research.biomedcentral.com). Other inflammatory mediators are also abundant in CF airways – for instance, IL-8 (CXCL8) is a neutrophil chemoattractant often found at high levels in CF sputum and BAL fluid, perpetuating neutrophil influx (respiratory-research.biomedcentral.com). TNF-α and IL-1β from immune cells contribute to the inflammatory milieu, and oxidative enzymes like myeloperoxidase (from neutrophils) generate oxidants that injure airway cells. Additionally, persistent bacteria in CF airways (such as Pseudomonas aeruginosa) produce virulence factors (e.g. alginate in mucoid Pseudomonas) that further thicken mucus and evade host defenses, though bacteria are not “molecular players” in the human sense, their presence is integral to disease mechanisms. In the gastrointestinal tract, digestive enzymes (pancreatic proteases, lipases) and bicarbonate transporters are downstream players affected by CFTR loss – for instance, the pancreatic ductal Cl⁻/HCO₃⁻ exchanger (SLC26A6) works in concert with CFTR, and without CFTR function, bicarbonate secretion is inadequate, leading to enzyme precipitation and duct blockage (pmc.ncbi.nlm.nih.gov).
It should also be noted that a revolution in therapy has introduced CFTR modulator drugs – small molecules that target the CFTR protein defects. These include ivacaftor (VX-770), a CFTR potentiator that increases channel opening for certain gating mutants (like G551D) (www.nature.com), and correctors like lumacaftor (VX-809), tezacaftor (VX-661), and elexacaftor (VX-445) that help misfolded F508del CFTR fold and traffic to the membrane (www.nature.com). The latest approved combination, elexacaftor/tezacaftor/ivacaftor (brand name Trikafta), can restore significant CFTR function in cells with the F508del mutation and others (www.nature.com). While these drugs are therapeutic (see section on real-world implementation), they are also important molecular tools that validate CFTR as the central player in CF pathogenesis – partial restoration of CFTR activity by modulators dramatically improves the cellular ion transport and thus the disease manifestations (www.nature.com). This underscores CFTR’s key role in all downstream pathological processes.
Chemical Entities: Several ions and small molecules are directly involved in CF pathophysiology. The most fundamental are chloride (Cl⁻) and sodium (Na⁺) ions. Chloride is the primary ion whose transport is disrupted by CFTR mutations – normally, CFTR allows Cl⁻ to exit epithelial cells into secretions (airway surface liquid, pancreatic fluid, sweat, etc.). In CF, chloride is trapped inside cells, leading to low chloride and water content in secretions and high sweat chloride on the skin surface (since sweat ducts cannot reabsorb Cl⁻) (pmc.ncbi.nlm.nih.gov). Sodium absorption through ENaC is the counterpoint: CFTR dysfunction leads to hyperactive Na⁺ uptake, which drags water out of mucus. The imbalance of Cl⁻ and Na⁺ movement causes hyperconcentrated mucus with high salt concentration but low water content (pmc.ncbi.nlm.nih.gov). Bicarbonate (HCO₃⁻) is another critical ion: CFTR conducts bicarbonate or regulates its secretion via other channels. Bicarbonate helps maintain an alkaline pH and proper unfolding of mucins. In CF, bicarbonate transport is reduced, leading to more acidic secretions. This impairs mucin expansion – mucins secreted by goblet cells are densely packed granules that require bicarbonate-rich fluid to swell and form a normal gel. Without sufficient HCO₃⁻, mucus remains dense and sticky (pmc.ncbi.nlm.nih.gov). A landmark experiment showed that in CF mice, intestinal mucus remained attached and impermeable, but adding a high concentration of bicarbonate restored mucus properties to normal (pmc.ncbi.nlm.nih.gov). In other words, “CF is caused by a nonfunctional chloride and bicarbonate ion channel (CFTR),” and loss of bicarbonate secretion is a key link to the “stagnant mucus” phenotype of the disease (pmc.ncbi.nlm.nih.gov) (PMID: 22711878). Thus, bicarbonate deficiency in CF secretions contributes to mucus pathology and perhaps to a more acidic airway surface that impairs antibacterial defenses (airway surface liquid pH is often lower in CF, reducing the activity of antimicrobial peptides). Water (H₂O) is indirectly the key molecule being mis-regulated; CFTR dysfunction results in dehydration of airway surface liquid. Hydration status of mucus is essentially the outcome of ion movement, so water is crucial for the rheology of secretions. ATP is another molecule of note: CFTR is an ATP-gated channel, and CFTR mutations like F508del affect ATP binding and hydrolysis cycle of the channel. cAMP (cyclic AMP) is the second messenger that activates PKA to open CFTR; thus cAMP levels and signaling (e.g. via β₂-adrenergic receptors) play a role in modulating CFTR activity. Pharmacologically, several small-molecule drugs interact with these pathways: e.g., Ivacaftor (CHEBI:64288) increases the probability of the CFTR channel being open (especially effective for Class III gating mutants) (www.nature.com). Corrector drugs (lumacaftor, tezacaftor, elexacaftor) are chemical chaperones that bind CFTR during folding. Other chemical entities relevant to CF include antibiotics (like tobramycin, aztreonam, etc., used to suppress airway infections) and mucolytics (e.g. dornase alfa, a DNAse enzyme that digests extracellular DNA in sputum). While these therapeutic agents are not part of the pathophysiology per se, their development was informed by understanding CF’s molecular mechanisms. Additionally, ions in sweat (Cl⁻ and Na⁺) serve as diagnostic chemicals: CF patients classically have sweat chloride concentrations >60 mmol/L (normal <30), often accompanied by high sodium, which can lead to salt depletion episodes in hot climates if not managed.
Cell Types: CF pathophysiology involves several cell types, chiefly epithelial cells of various organs. In the lungs, the critical cells are the ciliated respiratory epithelial cells (airway lining cells) that express CFTR on their apical surface. These include bronchiolar and bronchial epithelial cells (CL:0000066) that have motile cilia and interspersed goblet cells (mucus-secreting cells). CFTR is also highly expressed in the submucosal gland cells of the airways (submucosal glands produce a significant portion of airway mucus, especially in larger airways). Dysfunction of CFTR in these cell types leads to dehydrated periciliary fluid and mucus, and the glands produce mucus that is too concentrated. In the pancreas, the relevant cells are pancreatic duct epithelial cells (which normally secrete bicarbonate-rich fluid via CFTR) and acinar cells (which secrete digestive enzymes). Acinar cells themselves don’t express much CFTR, but their enzyme secretions cannot be flushed out without ductal fluid; thus, duct obstruction secondarily damages acinar cells. In the intestine, enterocytes and goblet cells of the intestinal mucosa (especially in the distal ileum and proximal colon) are affected – goblet cells produce abnormal mucus and enterocytes struggle with salt/fluid transport, causing thick stool. In the biliary tract, cholangiocytes (bile duct epithelial cells) rely on CFTR for bile fluid secretion; loss of CFTR causes bile precipitates and damage to these cells. In sweat glands, ductal epithelial cells fail to reabsorb salt. In the reproductive tract, the epididymal and vas deferens epithelial cells require CFTR for normal duct development and fluid balance; CFTR loss leads to atrophy or agenesis of the vas deferens in male fetuses.
Beyond epithelial cells, immune and inflammatory cells play a major role in CF lung pathology. Neutrophils (PMNs) are the dominant inflammatory cells in CF airways – they migrate into the bronchi in huge numbers in response to infection and CFTR-related dysregulation of inflammation. Neutrophils in CF may be functionally altered; for example, CFTR is expressed in leukocytes at low levels, and intrinsic CFTR dysfunction in immune cells might contribute to an overly aggressive but ineffective inflammatory response (some studies suggest CF neutrophils have impaired bacterial killing but excessive release of proteases and extracellular traps). Macrophages are also present in CF lungs and can ingest bacteria, but in CF they show impaired phagocytosis and altered cytokine profiles (possibly due to the chronic inflammatory environment). T-lymphocytes and other immune cells are involved to a lesser extent, with a biased Th17 and Th2 response noted in CF airways chronically. In CF-related diabetes, pancreatic islet β-cells are eventually destroyed by autoimmunity and fibrotic damage. In CF liver disease, hepatic stellate cells may be activated by bile duct injury to produce fibrosis. However, the primary cell-type focus of CF pathogenesis is the polarized epithelial cell in various organs, as that is where CFTR resides and its loss initiates downstream pathology.
Anatomical Locations: CF is a multi-organ disease, but certain anatomic sites are particularly impacted:
- Lungs (UBERON:0002048) – especially the bronchi and bronchioles of the respiratory tract. The entire airway tree from the trachea to small bronchioles is affected by thick mucus. Bronchioles are often the earliest sites of obstruction (leading to air trapping and collapse of distal alveoli). Over time, major airways develop bronchiectasis (dilated, damaged airways). The upper respiratory tract (nasal passages and paranasal sinuses) is also affected, with chronic sinusitis and nasal polyposis common.
- Pancreas (UBERON:0001264) – mainly the exocrine pancreas. The pancreatic ducts (which normally carry digestive enzymes and bicarbonate) are obstructed by viscid secretions, leading to pancreatic tissue destruction. The endocrine pancreas can also be affected secondarily, leading to CF-related diabetes.
- Gastrointestinal tract – particularly the small intestine (UBERON:0002108) at the ileum and the colon. Newborns with CF may have meconium ileus (obstruction at the distal ileum/ileocecal region). Throughout life, CF patients can suffer distal intestinal obstruction syndrome (DIOS) in the ileocecal area due to thick stool. The intestinal mucosa in CF also exhibits abnormal ion transport, which can cause constipation or obstruction if not managed.
- Hepatobiliary system – the bile ducts in the liver (intrahepatic bile ducts and extrahepatic ducts) can become clogged by thick secretions. This can cause focal biliary fibrosis and cirrhosis in the liver (UBERON:0002107). The gallbladder and gallstones are also more frequent in CF due to altered bile composition.
- Sweat glands – specifically the eccrine sweat glands in the skin. The sweat gland ducts are unable to reabsorb salt in CF, which anatomically results in high salt content on the skin surface (clinically tested at the forearm sweat glands).
- Reproductive tract – in males, the vas deferens (UBERON:0003889) and epididymis do not develop properly or are obliterated early (CBAVD). The testes themselves are usually normal and produce sperm, but sperm have no exit due to the missing vas deferens. In females, the cervix may have thick mucus, and there may be reduced fertility, but the anatomy (uterus, ovaries) is preserved.
- Other organs: The lungs and pancreas are considered the principal affected organs with life-threatening manifestations, but CF can also affect the upper GI tract (e.g. GERD is common in CF, and CFTR is expressed in salivary glands and esophagus to some extent). The ears (middle ear) can have chronic otitis media, especially in children, partly due to Eustachian tube dysfunction from thick secretions. Bones are indirectly affected (CF patients often have low bone density due to malabsorption and chronic inflammation, leading to higher risk of fractures).
Overall, CF pathophysiology centers on epithelial dysfunction in specific anatomic sites leading to organ-specific disease: chronic lung disease, pancreatic insufficiency, hepatobiliary disease, etc., all unified by the common thread of CFTR mutation and abnormal mucus/secretions.
Cystic fibrosis perturbs numerous biological processes. Key Gene Ontology (GO) categories relevant to CF include:
Ion Transport and Homeostasis: The primary process affected is chloride transmembrane transport (GO:1902476) across epithelial cell membranes. CFTR normally mediates chloride ion export; in CF this process is defective (pmc.ncbi.nlm.nih.gov). Sodium ion transport (GO:0006814) is secondarily increased via ENaC hyperactivity (pmc.ncbi.nlm.nih.gov). Together, these disrupt epithelial fluid transport and ion homeostasis on airway surfaces and in ducts. Bicarbonate transport (part of GO:0015701 bicarbonate transport) is also impaired, contributing to altered pH of secretions (pmc.ncbi.nlm.nih.gov).
Water Transport and Secretion: Linked to ion movement, CF causes failure of water transport and fluid secretion in glands. Though water transport is passive, the GO process fluid secretion (GO:0007589) is broadly disrupted – e.g., pancreatic fluid and airway surface liquid are diminished. The result is dehydration of the mucus layer (no specific GO term for “airway surface liquid homeostasis”, but this involves processes of ion transport and water homeostasis GO:0055082).
Mucociliary Clearance: CF fundamentally deranges mucociliary transport (GO:0120195, the process by which cilia move mucus). Due to dehydrated mucus and ciliary dysfunction, the process of clearing inhaled particles and pathogens is defective. Ciliary beat frequency is reduced by factors like neutrophil elastase and the thick mucus environment (respiratory-research.biomedcentral.com). Thus, epithelial cilium movement involved in mucociliary clearance (GO:0003351) is adversely affected in CF.
Mucin Production and Secretion: CF triggers abnormal mucin metabolic processes. Goblet cell differentiation and mucin secretion (GO:0070254 secretion by goblet cells) can be increased as a reactive process, leading to goblet cell hyperplasia. CF airway epithelial cells often show an upregulation of mucin genes (like MUC5B, MUC5AC) and produce mucus that is hyperconcentrated (respiratory-research.biomedcentral.com). Mucin packing/unfolding is disrupted due to lack of bicarbonate, meaning the process of mucin expansion upon secretion is incomplete (pmc.ncbi.nlm.nih.gov). This is a critical and unique biological process bridging cellular secretion to extracellular mucus gel formation.
Protein Folding and Degradation: On a cellular level, mutations like F508del cause defects in protein folding (GO:0006457) and result in CFTR being retained in the endoplasmic reticulum and targeted for ER-associated degradation (ERAD). The misfolded CFTR is ubiquitinated and destroyed by the proteasome (related to GO:0006515, protein quality control for misfolded proteins). Therefore, CF epithelia experience an augmented activity of the unfolded protein response (GO:0030968) and proteostasis mechanisms as they attempt to handle mutant CFTR. These processes are part of the molecular pathogenesis (Class II mutations cause a trafficking block (pmc.ncbi.nlm.nih.gov)).
Signal Transduction: CFTR dysfunction can perturb signaling pathways. For instance, CFTR has been implicated in regulating lung inflammation signaling. NF-κB signaling (GO:0051092) in CF cells may be heightened due to persistent infection and intrinsic stress, leading to increased cytokine production (IL-8, etc.). The lack of CFTR has been suggested to alter Toll-like receptor signaling in airway cells, possibly making them hyper-responsive to bacterial components. Additionally, cAMP-mediated signaling (GO:0019933) is central to CFTR regulation; in CF, even if cAMP is present, the effector (CFTR channel opening) is ineffective.
Immune and Inflammatory Response: CF lung disease involves chronic activation of innate immune response (GO:0045087). Neutrophil chemotaxis (GO:0030593) to the lungs is a prominent process – CF airways produce high levels of chemokines (like IL-8) recruiting neutrophils (respiratory-research.biomedcentral.com). The inflammatory response (GO:0006954) becomes dysregulated: neutrophils release excessive proteases and ROS, causing tissue damage. The normal resolution of inflammation is impaired, partly because neutrophils in CF undergo NETosis (releasing neutrophil extracellular traps) and die, spilling DNA and proteases that further clog airways. So processes like neutrophil degranulation (GO:0043312) and NET formation are upregulated. Oxidative stress processes are also in play: neutrophils and other cells generate reactive oxygen species (hydrogen peroxide, hypochlorous acid via myeloperoxidase) in excess, leading to oxidative damage to proteins and DNA in the lung.
Developmental Processes: CFTR is involved in certain developmental processes – notably development of the vas deferens. In CF males, the development of the Wolffian duct-derived structures (GO:0008584) is perturbed, leading to absent vas deferens (this is a developmental anomaly rather than a postnatal process). CFTR may also have roles in bone development and salt taste transduction, but those are less understood.
Metabolic Processes: Malabsorption from pancreatic insufficiency leads to altered nutrient metabolism. For instance, fat malabsorption causes deficiencies in fat-soluble vitamins (A, D, E, K) – affecting processes like vitamin K metabolic process (GO:0042373) and others, which manifests in coagulopathy or bone disease if not supplemented. CF-related diabetes involves the process of glucose homeostasis (GO:0042593) being disrupted due to insulin deficiency.
In summary, CF disrupts a broad network of biological processes: ion and fluid transport, mucociliary clearance, proteostasis, and immune responses are at the core of its pathophysiology. As Graeber & Mall (2023) note, understanding CF requires linking the molecular defect in CFTR to downstream processes like “mucus dysfunction, impaired host defenses, airway infection, and chronic inflammation” (pubmed.ncbi.nlm.nih.gov). Each of these processes corresponds to groups of GO terms that are highly relevant to CF and are prime targets for therapeutic intervention and research.
The pathological processes of CF can be mapped to specific cellular and subcellular locations (corresponding to GO Cellular Component terms):
Apical Plasma Membrane (GO:0016324): This is where the CFTR protein normally resides and functions. In epithelial cells lining ducts and airways, CFTR is localized to the apical membrane – the surface facing the lumen. CFTR’s role here is to transport chloride and bicarbonate out of the cell. In CF, the apical membrane has either no CFTR or a non-functional CFTR, so it fails to secrete chloride into the lumen (pmc.ncbi.nlm.nih.gov). The epithelial sodium channel (ENaC) is also on the apical membrane; in CF, ENaC activity becomes unrestrained at this location (pmc.ncbi.nlm.nih.gov). The cystic fibrosis defect is fundamentally at the apical membrane domain of epithelial cells, and many downstream issues (like thick mucus) manifest just beyond this membrane at the cell surface.
Airway Surface Liquid (Extracellular Fluid Layer): Just above the apical membrane of airway epithelial cells lies the thin layer of periciliary fluid and mucus – collectively the airway surface liquid (ASL), which is part of the extracellular region (GO:0005576). This is not a membrane-bound compartment but is crucial in CF. Normally ~7–10 μm thick, this liquid layer keeps mucus hydrated and allows cilia to beat. In CF, the ASL is depleted and hyperconcentrated (pmc.ncbi.nlm.nih.gov), leading to adherent mucus. The mucus itself (composed of secreted mucins, DNA, cell debris) accumulates in the airway lumen forming plaques and plugs (news.unchealthcare.org). These obstruct the bronchial lumen (anatomically) and functionally represent a pathological extracellular component in CF lungs. Mucus plugs often localize initially in small airways (bronchioles), which correspond to tiny luminal spaces that are easily occluded.
Secretory Granules (Golgi and Exocytic Pathway): Within goblet cells and submucosal gland cells, mucin granules are stored in secretory vesicles prior to exocytosis (GO:0030141, secretory granule lumen). In CF, the content of these granules (mucins) may be secreted normally, but due to acidic/low-volume extracellular environment, the mucins cannot expand properly and remain aggregated (pmc.ncbi.nlm.nih.gov). Additionally, the production of these granules can be upregulated due to chronic irritation. The CFTR protein itself during its biogenesis travels through the endoplasmic reticulum (GO:0005783) and Golgi apparatus (GO:0005794) in epithelial cells. For Class II mutations like F508del, CFTR is misfolded in the ER and targeted for degradation rather than reaching the Golgi. The proteasome (GO:0000502) in the cytosol is thus an important location in CF cells – it degrades mutant CFTR that fail quality control. CFTR that does fold correctly gets processed in the Golgi and delivered to the apical membrane via vesicles (GO:0030133, transport vesicle), but in CF patients with trafficking mutants, this delivery is inefficient or absent (pmc.ncbi.nlm.nih.gov).
Cell Surface and Tight Junctions: CFTR also interacts with other proteins at the cell surface, including components of tight junctions (GO:0005923). There is evidence CFTR may modulate tight junction permeability and that in CF, epithelial tight junctions could be abnormally tight or leaky influencing ion movement paracellularly. However, this is a minor aspect; the main issue at the cell surface is the absence of functional CFTR channel pores.
Lysosomes and Autophagosomes: Some studies suggest that CFTR dysfunction (particularly F508del) can lead to abnormalities in autophagy (GO:0006914) and lysosomal function in cells. F508del CFTR misfolding has been linked to accumulation of protein aggregates that may stress the cell’s clearing systems, and dysfunctional autophagy has been observed in CF cell models, contributing to exaggerated inflammation. For instance, beyond the proteasomal degradation, some mutant CFTR may be routed to lysosomes (GO:0005764) for destruction. Restoring autophagy in CF cells (e.g., by some small molecules) has been shown to improve CFTR trafficking in experimental systems. Thus, cytosolic compartments like the aggresome and autophagosome could be considered relevant in CF cellular pathology, although these are more on the research frontier.
Extracellular Space (Airway lumen and sputum): The extracellular space in CF airways is essentially the mucus layer and bronchoalveolar lining fluid. This space in CF becomes enriched with DNA from neutrophils (due to NETs and cell lysis), actin, filamentous polymers, and it is where bacteria reside as biofilms. DNA and filamentous actin significantly increase sputum viscosity. Clinically, the DNA in this extracellular space is targeted by the drug dornase alfa (recombinant DNase) to improve mucus rheology. Also, extracellular DNA and proteins (like neutrophil elastase) in CF sputum bind to protease inhibitors and reduce their effectiveness (respiratory-research.biomedcentral.com), essentially making the extracellular milieu highly proteolytic and pro-inflammatory.
Specific organ structures: In the pancreas, thick secretions accumulate within the pancreatic ducts (small interlobular ducts) – effectively an extracellular (duct lumen) issue, leading to intraductal precipitates and eventual fibrotic replacement of exocrine tissue. In the sweat gland ducts, the cellular component of interest is the ductal lumen where chloride reabsorption fails – high salt remains in the duct lumen and is excreted. In the vas deferens, the lumen either never forms or is obliterated by secretions in utero; anatomically, the vas deferens is usually absent or fibrosed in CF (so technically the cellular component is lost entirely in that case).
In summary, CF pathophysiology can be visualized at the cellular level as a defect at the apical membrane of epithelial cells leading to downstream changes in the extracellular environment (thick mucus in lumens). Key subcellular sites include the ER (where mutant CFTR misfolds), Golgi (trafficking), proteasomes (degradation of CFTR), and the airway surface liquid layer (which becomes dehydrated). By considering these cellular components, researchers design targeted interventions – for example, CFTR modulators aim to get CFTR to the apical membrane, osmolyte therapies (hypertonic saline, Mannitol) aim to rehydrate the airway surface liquid, and DNase targets the extracellular DNA in mucus. Each of these therapies corresponds to a cellular/extracellular compartment involved in CF disease.
Initiation and Early Pathogenesis: Cystic fibrosis begins in utero with the expression of mutant CFTR; by birth, certain manifestations can appear (e.g. meconium ileus in 15–20% of newborns with CF). The disease process is ongoing even in asymptomatic newborns. With universal newborn screening in many countries, most infants are now diagnosed within the first month of life (often before signs appear) (pmc.ncbi.nlm.nih.gov). However, studies of infants diagnosed via screening have shown that lung disease is present early. For instance, bronchoalveolar lavage studies in young infants (ages ~3 months) have found neutrophilic inflammation and elevated neutrophil elastase even in those without prior infections (respiratory-research.biomedcentral.com). Sly et al. (2009) observed that some infants with CF have detectable airway changes (air trapping, inflammation) on CT scans at a few months old (respiratory-research.biomedcentral.com). These findings indicate that CF lung disease often starts in the first months of life with a sterile neutrophilic inflammation (possibly due to an inherently abnormal airway environment) (respiratory-research.biomedcentral.com). Thus, the initial trigger of disease is the intrinsic ion transport defect leading to mucus stasis, which can provoke an inflammatory response even in the absence of infection (so-called “primary inflammation” of CF airways (www.nature.com)).
Early childhood: As infants grow into toddlers, they begin to experience respiratory symptoms. By age 1–2, many CF children develop a chronic cough. Early airway colonization occurs – Staphylococcus aureus is often found in CF infants’ airways, and other microbes follow. With each viral cold or bacterial infection, a pulmonary exacerbation can occur (worsening cough, increased sputum, difficulty breathing). These acute events accelerate damage. The pancreatic insufficiency, if present, manifests in infancy as malabsorption: frequent, oily stools, failure to thrive, and abdominal distension. With pancreatic enzyme replacement therapy, nutrition can be supported, but if untreated, malnutrition and vitamin deficiencies would progress. The hepatic manifestations are usually silent in infancy (liver disease tends to occur later, though some infants might have elevated liver enzymes). Sinus disease may begin early but is harder to detect (chronic nasal congestion). During early childhood, if aggressive therapy is given (airway clearance techniques, antibiotics, enzymes), lung function can be maintained near normal. However, airway remodeling may already be underway: by a few years old, some children show bronchiectasis on CT scans (respiratory-research.biomedcentral.com). This indicates that the window for preventing permanent lung damage is very early – reinforcing why early intervention is crucial.
Late childhood to adolescence: By school age (5–10 years), most CF patients historically acquired persistent colonization with Pseudomonas aeruginosa, a milestone that often marks an acceleration in lung decline. Chronic Pseudomonas infection is associated with biofilm formation in airways and a more intense neutrophilic inflammation. Clinically, children might start needing daily respiratory therapies (chest physiotherapy, nebulized antibiotics, mucolytics). Lung function (FEV₁) may start to decline measurably in late childhood, especially if chronic infections are established. Exacerbations (episodes of increased cough, sputum, and lung function drop) tend to become more frequent with age. Each exacerbation can cause a step-wise loss in lung function that might not fully recover post-treatment. By the teen years, many CF patients have moderate lung disease with bronchiectasis evident on imaging and FEV₁ trending down. Adolescence also brings CF-related diabetes onset in some patients (as pancreatic islets suffer damage); glucose intolerance often emerges by late teens or early adulthood in CF patients, especially those with pancreatic insufficiency and longer survival. Puberty can be delayed in CF due to chronic illness and malnutrition, and growth spurts might be blunted – many teens with CF have lower BMI percentiles despite enzyme supplementation, due to the high caloric needs and chronic inflammation.
Adulthood and Late-stage disease: Historically, many CF patients did not survive to adulthood, but with modern care, over 50% of CF individuals in developed countries are adults (pmc.ncbi.nlm.nih.gov). The adult phase of CF is often dominated by progressive lung decline. By early adulthood (20s to 30s), patients without highly effective therapy often have significant bronchiectasis in all lobes, chronic hypoxemia, and frequent exacerbations requiring intravenous antibiotics (tune-ups). Many develop complications like hemoptysis (coughing up blood) due to inflamed bronchial arteries in dilated airways, or pneumothorax (lung collapse) due to ruptured cystic airspaces. The endocrine manifestations like CF-related diabetes become more common (~40–50% of adults over 30 with CF have CFRD). Osteoporosis may occur prematurely due to malabsorption and steroid use for inflammation. In a subset, liver cirrhosis progresses to cause portal hypertension, varices, and risk of liver failure in late teens or adulthood. Male infertility is typically an issue when adult CF patients consider having children – since nearly all males have azoospermia, many pursue assisted reproductive techniques with sperm aspiration if they wish to father children. Psychosocially, adults with CF deal with managing a chronic illness – frequent hospitalizations for lung infections, and possibly lung transplant evaluation when lung function falls below ~30% predicted. Terminal stage CF lung disease is characterized by respiratory failure, often in the 3rd or 4th decade of life in classic cases: patients become dependent on oxygen and have hypercapnia due to inadequate ventilation from destroyed airways. Without intervention, this results in death from respiratory failure or cor pulmonale. Lung transplantation is a life-extending option at this stage, and CF is one of the most common indications for lung transplant in young adults.
Distinct Phases: One can describe CF progression in clinical stages: an early stage (often asymptomatic newborn identified by screening), a mild symptomatic stage in early childhood (where interventions can maintain near-normal lung function), a moderate stage in adolescence (chronic infection is established, lung function decline begins), and a severe stage in adulthood (advanced lung disease with complications and consideration of transplant). Another perspective is organ-specific staging: for lungs, clinicians sometimes use lung function (FEV₁ % predicted) to stage disease (mild if >70%, moderate 40–69%, severe <40%). For example, a child might be in a “mild lung disease stage” and later progress to “severe lung disease stage.” CF progression is also sometimes discussed as pre- and post-CFTR modulator eras, which we address below.
Impact of New Therapies: It is critical to note that recent developments (2019–2024) have dramatically altered the typical disease trajectory for many patients. The advent of CFTR modulator therapies, especially the triple-combination modulator (elexacaftor/tezacaftor/ivacaftor) approved in 2019, has changed the progression for those eligible (roughly 85–90% of CF patients with at least one F508del allele) (www.nature.com). These modulators partially restore CFTR function at the cellular level, thereby improving ion transport and hydrating secretions. Clinically, patients on highly effective modulators have shown rapid improvements: for example, a mean increase of 10-14 percentage points in FEV₁, weight gain, reduced sweat chloride, and ~60% fewer pulmonary exacerbations in trials (www.nature.com) (www.nature.com). Real-world data in 2021–2023 confirm fewer hospitalizations and dramatic improvements in quality of life for modulator-treated patients. As a result, many patients who, prior to modulators, would be in a downward spiral of lung function in their 20s are now experiencing stabilization or even improvement of lung function. Some adults with advanced disease have been able to avoid or delay lung transplant due to modulator therapy. The long-term disease progression on modulators is still being studied, but current evidence shows slower FEV₁ decline and possible amelioration of some organ damage if started early. For instance, children starting modulators before significant lung damage may potentially never develop severe bronchiectasis. It is conceivable that CF could become a much more benign disease for most patients, with survival extending further. Indeed, “the introduction of a highly effective triple combination CFTR modulator therapy that has unprecedented clinical benefits in ~90% of eligible people with CF has fundamentally changed the therapeutic landscape and improved prognosis” (www.nature.com). However, challenges remain: ~10% of CF patients (those with rare CFTR mutations not responsive to current modulators or with end-stage complications) still face a high burden of disease and need alternative therapies (www.nature.com). Additionally, any established lung damage (fibrosis, bronchiectasis) cannot be fully reversed by modulators, so early intervention is key.
Life Expectancy Trends: As a measure of disease progression at the population level, life expectancy in CF has steadily improved over decades. In 1938 when CF was first described, it was invariably fatal in infancy or early childhood (pmc.ncbi.nlm.nih.gov). By the 1980s, median survival was into the teens. By the 2000s, median predicted survival was late 30s. Currently, in the US and many developed countries, median survival is estimated to be around 44–50 years (pmc.ncbi.nlm.nih.gov), and children born today with CF are expected to live into mid-adulthood and beyond, especially if they have access to modulators. For example, the Cystic Fibrosis Foundation patient registry (USA) reported a median life expectancy of ~50 years for those born in recent years, a number that will likely be revised upward as the full impact of modulator therapy is realized (pmc.ncbi.nlm.nih.gov). It’s worth noting that progression and outcomes still vary individually: factors like genotype, adherence to therapy, access to specialized CF care, and social determinants can accelerate or slow disease progression (www.nature.com) (www.nature.com). For instance, individuals with residual CFTR function mutations (milder genotypes) might have a slower progression and later diagnosis (some not diagnosed until adulthood if they primarily have pancreatic-sufficient CF or atypical CF symptoms). On the other hand, patients with classic severe mutations who acquire aggressive infections early can still have a rapid decline if not effectively treated.
In summary, CF disease progression traditionally followed a relentless decline, especially in lung function, over 2–4 decades, with well-defined complications at various stages (infections in childhood, complications like CFRD and liver disease in adolescence, respiratory failure in adulthood). Now, with modern treatment, the trajectory is improving – early-life interventions (newborn screening, prophylactic care) aim to delay or prevent the establishment of chronic lung disease, and CFTR modulators aim to correct the basic defect and alter the natural history. The goal is that future CF patients might not experience the classic severe “late stage” at all, effectively transforming CF into a chronic manageable condition with normal or near-normal lifespan (pubmed.ncbi.nlm.nih.gov) (pubmed.ncbi.nlm.nih.gov). Ongoing research in gene therapy and gene editing holds the hope of an eventual cure that could halt disease progression at the causal level for all patients (pubmed.ncbi.nlm.nih.gov).
Cystic fibrosis has a well-defined clinical phenotype with multisystem involvement. Many of the hallmark clinical features of CF are direct consequences of the underlying molecular and cellular defects described above. Key phenotypic manifestations include:
Chronic Pulmonary Disease: Virtually all CF patients develop progressive lung disease. Clinically, this presents as chronic cough (often productive of thick sputum), wheezing, and recurrent respiratory infections (bronchitis or pneumonia). Over time, these recurrent infections lead to chronic colonization of the lungs with bacteria (e.g. Pseudomonas aeruginosa, Burkholderia cepacia complex, Staphylococcus aureus), and patients experience intermittent pulmonary exacerbations characterized by increased cough, sputum, shortness of breath, and often fevers. One distinctive manifestation is bronchiectasis – pathological dilation of bronchi – which on high-resolution CT scans appears in most CF patients by adolescence. Bronchiectasis is responsible for persistent moist crackles on lung exam and contributes to further mucus pooling. Digital clubbing (enlargement of fingertips) is commonly observed in CF (HP:0001217), believed to result from chronic hypoxia and inflammation in the lungs. As lung disease advances, patients can develop hypoxemia (low blood oxygen) requiring supplemental oxygen, and signs of respiratory failure or cor pulmonale (right heart failure due to lung disease) in late stages. The connection to pathophysiology: these respiratory phenotypes arise because CFTR dysfunction led to thick mucus that causes infection/inflammation, which in turn yields the symptoms of cough, sputum, and lung damage. Importantly, muco-obstructive exacerbations are a key phenotype; they often require intravenous antibiotics and intensified therapy. The severity of lung involvement is often quantified by FEV₁ (forced expiratory volume in 1s) – a phenotype measurable by spirometry. CF patients typically show obstructive lung physiology on PFTs, with reduced FEV₁ that declines with age (absent intervention). For example, without modulators, the median FEV₁ in CF might decline by ~1-3% predicted per year in young adulthood. With modulators, this decline is attenuated. Clinical scoring systems like the Bhalla score on CT or the Shwachman-Kulczycki score historically summarized the pulmonary phenotype severity.
Exocrine Pancreatic Insufficiency: ~85% of CF patients have pancreatic insufficiency (HP:0001738) from infancy or early childhood. This manifests as steatorrhea (bulky, greasy, foul-smelling stools due to fat malabsorption), failure to thrive or poor weight gain in infancy (HP:0001508), protuberant abdomen, and deficiency of fat-soluble vitamins (leading to e.g. vitamin K deficiency coagulopathy or vitamin D deficiency rickets if untreated). Parents may notice infants with CF have frequent, oily diarrhea and voracious appetites but poor growth. Pancreatic insufficiency is due to the blockage and autolysis of pancreatic tissue in utero/early life, as described in pathophysiology. It is effectively managed by pancreatic enzyme replacement capsules and high-calorie diets, which has greatly improved nutritional phenotypes. Still, even with enzyme supplements, many CF patients struggle to maintain normal body mass; the phenotype of malnutrition (low BMI) correlates with worse lung outcomes. A small subset (~15%) of CF patients have milder CFTR mutations allowing some pancreatic function – they are pancreatic-sufficient and may have near-normal digestion (sometimes not diagnosed until later in life due to lack of malabsorption symptoms). However, even pancreatic-sufficient CF patients can develop pancreatitis as an episodic phenotype (recurrent acute pancreatitis occurs in some CFTR mutations, especially those associated with CFTR-related disorders).
Meconium Ileus and Gastrointestinal Obstruction: In neonates, meconium ileus (HP:0005109) is a classic CF phenotype – about 15% of CF newborns present within the first 48 hours of life with intestinal obstruction by abnormally thick meconium in the ileum (pmc.ncbi.nlm.nih.gov). This often requires contrast enema or even surgery (it can lead to perforation if untreated). Its presence at birth is highly suggestive of CF. Later in life, older children and adults can experience a similar blockage called Distal Intestinal Obstruction Syndrome (DIOS), where thick stool causes obstruction at the ileocecal junction. Symptoms include abdominal pain, distension, and absence of stool passage. CF patients also have a higher incidence of intussusception in childhood (telescoping of the bowel) likely related to thick stool acting as a lead point. GERD (acid reflux) is more common in CF, possibly due to increased abdominal pressure from coughing and anatomic changes; reflux can in turn exacerbate lung issues by microaspiration. Over years, some CF patients develop gastrointestinal manifestations like CF-related liver disease – often first noted as hepatomegaly or abnormal liver enzymes in childhood. About 5-7% develop cirrhosis with portal hypertension (esophageal varices, splenomegaly) typically in adolescence. This “CF liver disease” phenotype can lead to complications requiring interventions (endoscopy for varices, even liver transplant in ~1-2% of patients). Gallbladder involvement (like gallstones or microgallbladder) is also noted as a phenotype in some CF adults.
Sweat Abnormalities: CF patients have salty sweat, which is usually noticed by parents (“kissing the baby tastes salty”). The sweat test is a formal measurement of this phenotype: nearly all individuals with classic CF have sweat chloride >60 mM on a pilocarpine iontophoresis test (normal is <30) (pmc.ncbi.nlm.nih.gov). This is not just diagnostic; it can have clinical consequences – CF infants can develop hyponatremic dehydration in hot weather if salt intake isn’t increased, a phenomenon first described in the 1940s (pmc.ncbi.nlm.nih.gov). Some CF patients (especially those with milder mutations) have intermediate sweat chloride levels (30–60 mM) and may be diagnosed after newborn screening or later in life with atypical CF; sweat test remains a key phenotype bridging the molecular defect (CFTR in sweat ducts) to a clinical sign.
ENT Manifestations: Chronic sinusitis is present in most CF patients (HP:0000246 for chronic sinusitis). They often have nasal congestion, sinus headaches, and about 10-20% develop nasal polyps (HP:0100574) at a young age that may require surgical removal (pmc.ncbi.nlm.nih.gov). The presence of nasal polyps in a child is a clinical red flag for CF. Middle ear infections (otitis media) are also more frequent in CF children.
Male Infertility: More than 95% of males with CF are infertile due to azoospermia (absence of sperm in ejaculate) caused by the congenital absence of the vas deferens (HP:0000037). This phenotype is often how CFTR mutations are discovered in men with otherwise mild or no lung disease (CBAVD can be an isolated manifestation of CFTR-related disorder). In CF patients, this is typically known from adolescence. Females with CF have normal fertility potential, though reduced if ill; however, in the era of better health, many women with CF conceive successfully (with higher-risk pregnancies due to cardiorespiratory strain).
CF-Related Diabetes (CFRD): By adulthood ~30-50% of CF patients develop a unique form of diabetes (HP:0004904) caused by insulin insufficiency from pancreatic damage, often compounded by peripheral insulin resistance from infection and steroid use. CFRD clinically resembles type1 & type2 hybrid – patients may have polyuria, polydipsia, weight loss, or just declining lung function as a clue. This phenotype typically appears in late adolescence or adulthood and requires insulin therapy.
Musculoskeletal: Many CF patients, especially older, have low bone density (osteopenia/osteoporosis) due to malabsorption of vitamin D and chronic inflammation. This can lead to fractures or kyphosis (spinal curvature) in advanced disease. Also, muscle mass may be low due to catabolic illness. Clubbing of fingers (a musculoskeletal change of the nail beds) has been mentioned and is very common in CF lung disease (often evident by childhood).
Other systemic manifestations: Some CF patients develop allergic bronchopulmonary aspergillosis (ABPA) – an allergic immune response to Aspergillus fungus in the lungs, causing wheezing and pulmonary infiltrates; this is a complicating phenotype in ~10% of CF individuals. Another complication is amyloidosis (rarely) from chronic inflammation. Depression and anxiety are noted at higher rates in CF populations as comorbid mental health phenotypes due to the stress of chronic disease.
To succinctly connect to mechanisms: “CF is characterized by pulmonary manifestations (chronic obstructive lung disease with infection and bronchiectasis), sinusitis, malabsorption due to pancreatic exocrine insufficiency, liver disease (biliary cirrhosis), CF-related diabetes, and male infertility” (pmc.ncbi.nlm.nih.gov) (PMID: 33526571). Each of these clinical phenotypes is a direct consequence of CFTR dysfunction in the respective organ: lung disease from mucus obstruction and infection, digestive malabsorption from pancreatic blockage, etc. The severity of phenotypes can vary: for example, patients with “mild” CFTR mutations might present with only infertility and mild lung issues in late adulthood (atypical CF), whereas classic CF with no functional CFTR causes the full spectrum early in life.
Relevant Statistics: Before modulator therapies, lung disease caused 80-95% of CF mortality. The median age of survival in CF has improved to ~44 years in recent reports (pmc.ncbi.nlm.nih.gov), and it is projected to continue rising with widespread modulator use. Over 90% of CF patients have at least one copy of F508del mutation, which explains why triple modulator therapy can benefit about 90% of the CF population (www.nature.com). The introduction of these modulators has led to a 63% reduction in annualized pulmonary exacerbation rate in clinical trials for elexacaftor/tezacaftor/ivacaftor (www.nature.com) and significant improvements in BMI and quality of life scores. Newborn screening (NBS) has led to early diagnosis (median age of diagnosis in screened regions is <1 month). Thanks to NBS and proactive care, many CF children now have normal growth and only mild lung function decrement by age 6–10 (e.g., an Australian study showed mean FEV₁ ~100% at age 7 in screened cohorts) . However, disparities exist: CF patients of minority backgrounds may have rarer CFTR mutations not detectable by standard screens and may be diagnosed late (www.nature.com), and access to modulators is uneven globally. These factors can influence phenotype expression and outcomes.
In conclusion, the phenotypic spectrum of cystic fibrosis spans respiratory, gastrointestinal, endocrine, and reproductive systems, with chronic progressive lung disease being the most prominent feature linking to mortality. The classic clinical picture includes a child with chronic cough and lung infections, malabsorption with poor growth, and salty-tasting skin, and later complications like diabetes and infertility. This clinical phenotype is directly traceable to the underlying pathophysiology at the molecular level, and ongoing advancements in therapy are dramatically improving these manifestations. As one 2023 review noted, CF has transformed “from a fatal disease to a treatable one” due to therapies addressing the root cause (pubmed.ncbi.nlm.nih.gov), giving hope that future phenotypes will be far milder than the historical description. Each clinical sign and complication of CF, when mapped back, underscores the importance of CFTR in diverse organs and the wide-ranging impact of its dysfunction on human physiology.
Evidence and References: (Key sources supporting the above information include primary literature and authoritative reviews. Citations are provided in text for specific claims: e.g., Dickinson & Collaco 2021, PMID: 33526571 for multi-organ manifestations (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov); Mall et al. 2024, PMID: 34385510 for CFTR function and lung disease emphasis (www.nature.com); Grasemann & Ratjen 2023, PMID: 37913507 for updated pathophysiology; Graeber & Mall 2023, PMID: 37699417 for advances since 2018 (pubmed.ncbi.nlm.nih.gov); Boucher 2019, PMID: 31067370 for muco-obstructive pathology (news.unchealthcare.org); Hobbs et al. 2013, PMID: 23878362 for ENaC hyperactivity (pmc.ncbi.nlm.nih.gov); Gustafsson et al. 2012, PMID: 22711878 for bicarbonate’s role in mucin release (pmc.ncbi.nlm.nih.gov); and a 2017 study by Gramegna et al., PMID: 29258516 highlighting neutrophil elastase-driven inflammation in CF lungs (respiratory-research.biomedcentral.com) (respiratory-research.biomedcentral.com).)
name: Cystic Fibrosis
creation_date: '2025-12-19T14:27:56Z'
updated_date: '2026-03-31T02:48:22Z'
description: >-
Cystic fibrosis is a common life-limiting autosomal recessive genetic disorder
caused by mutations in the CFTR gene encoding the cystic fibrosis transmembrane
conductance regulator, a chloride and bicarbonate channel expressed in epithelial
cells. CFTR dysfunction leads to dehydrated, viscous secretions in multiple organ
systems, most critically the airways and pancreas. Nearly 2,000 CFTR variants have
been identified, with the Phe508del (F508del) mutation present in nearly 90% of
patients. The disease is characterized by progressive bronchiectasis, chronic
bacterial lung infection, exocrine pancreatic insufficiency, male infertility due
to congenital bilateral absence of the vas deferens, and elevated sweat chloride.
Multidisciplinary care and CFTR modulator therapies have extended median survival
beyond 40 years, with the advent of elexacaftor-tezacaftor-ivacaftor (Trikafta)
representing a transformational advance for the majority of patients.
category: Genetic
parents:
- Respiratory Disease
- Inborn Error of Metabolism
prevalence:
- population: European descent
percentage: 1 in 2,500 to 3,500 live births
evidence:
- reference: PMID:27140670
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Cystic fibrosis is a common life-limiting autosomal recessive genetic
disorder, with highest prevalence in Europe, North America, and Australia."
explanation: Lancet seminar confirms highest CF prevalence in populations of
European descent.
- population: African American
percentage: 1 in 15,000 to 20,000 live births
evidence:
- reference: PMID:33526571
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Cystic fibrosis (CF) is one of the most commonly diagnosed genetic disorders."
explanation: Pediatric review confirms CF as a common genetic disorder with
variable prevalence across populations.
- population: Asian
percentage: 1 in 30,000 to 100,000 live births
evidence:
- reference: PMID:27140670
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Cystic fibrosis is a common life-limiting autosomal recessive genetic
disorder, with highest prevalence in Europe, North America, and Australia."
explanation: Lower prevalence in Asian populations is implied by highest
prevalence being in European-descent populations.
inheritance:
- name: Autosomal Recessive
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Cystic fibrosis (CF) is an autosomal recessive disease characterized
by pancreatic insufficiency and chronic endobronchial airway infection."
explanation: Clinical review confirms autosomal recessive inheritance
pattern.
definitions:
- name: CF Foundation Diagnostic Criteria (2017)
definition_type: CASE_DEFINITION
description: >-
Consensus guidelines from the Cystic Fibrosis Foundation for establishing a
diagnosis of CF in individuals from newborn to adult, requiring evidence of
CFTR dysfunction via sweat chloride testing combined with clinical features
or two disease-causing CFTR mutations.
scope: Diagnosis of cystic fibrosis in all age groups
criteria_sets:
- name: Diagnostic criteria for cystic fibrosis
description: >-
CF diagnosis requires clinical features consistent with CF in at least one
organ system OR positive newborn screen, PLUS evidence of CFTR dysfunction
demonstrated by elevated sweat chloride (>=60 mmol/L) or identification of
two CF-causing CFTR mutations.
core_clinical_characteristics:
- preferred_term: Elevated sweat chloride
term:
id: HP:0410017
label: Abnormal sweat electrolyte concentration
- preferred_term: Recurrent respiratory infections
term:
id: HP:0002205
label: Recurrent respiratory infections
- preferred_term: Exocrine pancreatic insufficiency
term:
id: HP:0001738
label: Exocrine pancreatic insufficiency
- preferred_term: Male infertility
term:
id: HP:0003251
label: Male infertility
- preferred_term: Meconium ileus
term:
id: HP:0004401
label: Meconium ileus
evidence:
- reference: PMID:28129811
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "It is recommended that diagnoses associated with CFTR mutations in all
individuals, from newborn to adult, be established by evaluation of CFTR function
with a sweat chloride test."
explanation: CF Foundation consensus guidelines establish sweat chloride
testing as the cornerstone of CF diagnosis.
- name: Newborn Screening Algorithm
definition_type: DIAGNOSTIC_CRITERIA
description: >-
Most CF cases in the US and many other countries are identified through newborn
screening (NBS) programs that measure immunoreactive trypsinogen (IRT) in dried
blood spots, followed by CFTR mutation panel or a second IRT measurement. Positive
screens require diagnostic confirmation with sweat chloride testing.
scope: Newborn screening for cystic fibrosis
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Most cases of CF are identified through newborn screening (NBS)."
explanation: Clinical review confirms newborn screening as the primary route
to CF diagnosis.
pathophysiology:
- name: CFTR Dysfunction
description: >-
Mutations in the CFTR gene reduce or eliminate CFTR channel function at
epithelial surfaces. Defective CFTR impairs epithelial anion and water
handling, creating dehydrated secretions that initiate respiratory,
gastrointestinal, hepatobiliary, sweat-gland, and reproductive disease.
cell_types:
- preferred_term: Epithelial cell
term:
id: CL:0000066
label: epithelial cell
biological_processes:
- preferred_term: Chloride Transport
modifier: DECREASED
term:
id: GO:0006821
label: chloride transport
- preferred_term: bicarbonate transport
modifier: DECREASED
term:
id: GO:0015701
label: bicarbonate transport
evidence:
- reference: PMID:9922375
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "The cystic fibrosis transmembrane conductance regulator (CFTR) is a
unique member of the ABC transporter family that forms a novel Cl- channel.
It is located predominantly in the apical membrane of epithelia where it mediates
transepithelial salt and liquid movement. Dysfunction of CFTR causes the genetic
disease cystic fibrosis."
explanation: Comprehensive review establishes CFTR as chloride channel whose
dysfunction causes cystic fibrosis.
- reference: PMID:9922375
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "The CFTR is composed of five domains: two membrane-spanning domains
(MSDs), two nucleotide-binding domains (NBDs), and a regulatory (R) domain."
explanation: Describes the five-domain architecture of CFTR critical to
understanding mutation effects.
downstream:
- target: Airway Surface Liquid Depletion
description: Loss of epithelial chloride and bicarbonate secretion dehydrates
airway surface liquid.
evidence:
- reference: PMID:23878362
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "CF lungs are characterized by viscous, dehydrated mucus, persistent
neutrophilia and chronic infections. ENaC is negatively regulated by CFTR and,
in patients with CF, the absence of CFTR results in a double hit of reduced
Cl-/HCO3- and H2O secretion as well as ENaC hyperactivity and increased Na+
and H2O absorption."
explanation: CFTR loss with reduced Cl-/HCO3- secretion is linked to airway
dehydration.
- target: ENaC Hyperactivity and Sodium Hyperabsorption
description: Loss of CFTR-mediated inhibition increases ENaC-dependent sodium
and water absorption.
evidence:
- reference: PMID:23878362
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "CF lungs are characterized by viscous, dehydrated mucus, persistent
neutrophilia and chronic infections. ENaC is negatively regulated by CFTR and,
in patients with CF, the absence of CFTR results in a double hit of reduced
Cl-/HCO3- and H2O secretion as well as ENaC hyperactivity and increased Na+
and H2O absorption."
explanation: Supports CFTR loss as an upstream cause of ENaC hyperactivity.
- target: Pancreatic Duct Obstruction
description: Viscid epithelial secretions obstruct pancreatic ducts and
initiate pancreatic injury.
evidence:
- reference: PMID:33526571
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Clinical characteristics include progressive obstructive lung disease,
sinusitis, exocrine pancreatic insufficiency leading to malabsorption and malnutrition,
liver and pancreatic dysfunction, and male infertility."
explanation: Supports pancreatic dysfunction as a core epithelial consequence
of CF.
- target: Intestinal Obstruction
description: Dehydrated intestinal secretions cause bowel obstruction.
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Other complications include sinusitis, diabetes mellitus, bowel obstruction,
hepatobiliary disease, hyponatremic dehydration, and infertility."
explanation: Supports bowel obstruction as a downstream complication of CFTR
dysfunction.
- target: Sweat Gland Dysfunction
description: Failure of sweat-duct chloride reabsorption raises sweat chloride.
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Diagnosis of CF is confirmed by demonstration of elevated sweat chloride."
explanation: Elevated sweat chloride supports sweat-duct ion-transport
dysfunction downstream of CFTR loss.
- target: Vas Deferens Agenesis
description: CFTR dysfunction contributes to male reproductive tract
abnormalities and infertility.
evidence:
- reference: PMID:33526571
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Clinical characteristics include progressive obstructive lung disease,
sinusitis, exocrine pancreatic insufficiency leading to malabsorption and malnutrition,
liver and pancreatic dysfunction, and male infertility."
explanation: Supports male infertility as a canonical downstream manifestation
of CF.
- target: Hepatobiliary Obstruction
description: Viscid bile causes biliary obstruction and hepatobiliary disease.
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Other complications include sinusitis, diabetes mellitus, bowel obstruction,
hepatobiliary disease, hyponatremic dehydration, and infertility."
explanation: Supports hepatobiliary disease as a downstream complication of
CF.
- target: Sinonasal Disease
description: Impaired epithelial ion and fluid transport promotes chronic
sinonasal disease.
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Other complications include sinusitis, diabetes mellitus, bowel obstruction,
hepatobiliary disease, hyponatremic dehydration, and infertility."
explanation: Supports sinusitis as a downstream clinical consequence.
- name: ENaC Hyperactivity and Sodium Hyperabsorption
description: >-
In CF airways, reduced CFTR function disinhibits ENaC, increasing epithelial
sodium and water absorption and worsening airway dehydration.
cell_types:
- preferred_term: Bronchial epithelial cell
term:
id: CL:0002328
label: bronchial epithelial cell
biological_processes:
- preferred_term: sodium ion transport
modifier: INCREASED
term:
id: GO:0006814
label: sodium ion transport
evidence:
- reference: PMID:23878362
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "CF lungs are characterized by viscous, dehydrated mucus, persistent
neutrophilia and chronic infections. ENaC is negatively regulated by CFTR and,
in patients with CF, the absence of CFTR results in a double hit of reduced
Cl-/HCO3- and H2O secretion as well as ENaC hyperactivity and increased Na+
and H2O absorption."
explanation: Supports ENaC hyperactivity and increased Na+/water absorption in
CF airway epithelium.
downstream:
- target: Airway Surface Liquid Depletion
description: Increased Na+/H2O absorption further depletes airway surface liquid.
evidence:
- reference: PMID:23878362
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "CF lungs are characterized by viscous, dehydrated mucus, persistent
neutrophilia and chronic infections. ENaC is negatively regulated by CFTR and,
in patients with CF, the absence of CFTR results in a double hit of reduced
Cl-/HCO3- and H2O secretion as well as ENaC hyperactivity and increased Na+
and H2O absorption."
explanation: Supports direct contribution of ENaC hyperabsorption to airway
dehydration.
- name: Airway Surface Liquid Depletion
description: >-
Reduced epithelial anion secretion together with increased sodium absorption
depletes the periciliary liquid layer and airway surface liquid.
cell_types:
- preferred_term: Bronchial epithelial cell
term:
id: CL:0002328
label: bronchial epithelial cell
biological_processes:
- preferred_term: mucus secretion
modifier: ABNORMAL
term:
id: GO:0070254
label: mucus secretion
locations:
- preferred_term: Lung
term:
id: UBERON:0002048
label: lung
evidence:
- reference: PMID:23878362
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "CF lungs are characterized by viscous, dehydrated mucus, persistent
neutrophilia and chronic infections. ENaC is negatively regulated by CFTR and,
in patients with CF, the absence of CFTR results in a double hit of reduced
Cl-/HCO3- and H2O secretion as well as ENaC hyperactivity and increased Na+
and H2O absorption."
explanation: Review describes ENaC hyperactivity and dehydration mechanism
in CF airways.
downstream:
- target: Impaired Mucociliary Clearance
description: Airway liquid depletion causes ineffective mucus transport and
mucus stasis.
evidence:
- reference: PMID:23878362
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Together, these effects are hypothesized to trigger mucus dehydration,
resulting in a failure to clear mucus."
explanation: Supports the mechanistic link between airway dehydration and
defective mucus clearance.
- name: Impaired Mucociliary Clearance
description: >-
Dehydrated airway surfaces reduce effective mucus transport, allowing mucus to
remain adherent on airway epithelium.
biological_processes:
- preferred_term: mucociliary clearance
modifier: DECREASED
term:
id: GO:0120197
label: mucociliary clearance
evidence:
- reference: PMID:23878362
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Together, these effects are hypothesized to trigger mucus dehydration,
resulting in a failure to clear mucus."
explanation: Supports impaired mucociliary clearance as a discrete downstream
step after airway dehydration.
downstream:
- target: Mucus Plugging
description: Failed mucus transport promotes adherent mucus plugging.
evidence:
- reference: PMID:27140670
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Functional failure of CFTR results in mucus retention and chronic infection
and subsequently in local airway inflammation that is harmful to the lungs."
explanation: Human clinical review supports airway mucus retention as a
direct downstream step toward mucus plugging.
- name: Mucus Plugging
description: >-
Impaired mucus transport generates concentrated, adherent mucus plugs that
persist in the airway lumen.
cell_types:
- preferred_term: Bronchial epithelial cell
term:
id: CL:0002328
label: bronchial epithelial cell
biological_processes:
- preferred_term: mucus secretion
modifier: ABNORMAL
term:
id: GO:0070254
label: mucus secretion
evidence:
- reference: PMID:22711878
supports: SUPPORT
evidence_source: MODEL_ORGANISM
snippet: "We show that the ileal mucosa in CF have a mucus that adhered to the
epithelium, was denser, and was less penetrable than that of wild-type mice."
explanation: Study demonstrates the mechanistic link between CFTR
dysfunction and abnormal mucus properties.
downstream:
- target: Small-Airway Obstruction
description: Luminal mucus plugs narrow and obstruct small airways.
evidence:
- reference: PMID:33526571
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Clinical characteristics include progressive obstructive lung disease,
sinusitis, exocrine pancreatic insufficiency leading to malabsorption and malnutrition,
liver and pancreatic dysfunction, and male infertility."
explanation: Supports progressive obstructive airway physiology as a downstream
consequence of CF airway disease.
- target: Chronic Bacterial Infection
description: Retained mucus supports persistent bacterial colonization and
chronic endobronchial infection.
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Cystic fibrosis (CF) is an autosomal recessive disease characterized
by pancreatic insufficiency and chronic endobronchial airway infection."
explanation: Supports progression from mucus retention to chronic airway
infection.
- name: Small-Airway Obstruction
description: >-
Progressive luminal obstruction and air trapping in small airways emerges from
persistent mucus plugging.
locations:
- preferred_term: Lung
term:
id: UBERON:0002048
label: lung
evidence:
- reference: PMID:33526571
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Clinical characteristics include progressive obstructive lung disease,
sinusitis, exocrine pancreatic insufficiency leading to malabsorption and malnutrition,
liver and pancreatic dysfunction, and male infertility."
explanation: Supports small-airway obstruction as a central respiratory disease
feature.
downstream:
- target: Bronchiectasis
description: Persistent obstruction contributes to irreversible airway structural
damage.
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "This latter feature results in progressive bronchiectasis and ultimately
respiratory failure, which is the leading cause of death in patients with CF."
explanation: Supports progression from chronic airway disease to bronchiectasis.
- name: Chronic Bacterial Infection
description: >-
The CF airway is chronically colonized by characteristic pathogens.
Staphylococcus aureus typically predominates in early childhood, followed by
Pseudomonas aeruginosa which becomes the dominant pathogen in adolescence and
adulthood. P. aeruginosa transitions to a mucoid phenotype with alginate
biofilm production, making eradication extremely difficult. Other important
pathogens include Burkholderia cepacia complex, Stenotrophomonas maltophilia,
Achromobacter xylosoxidans, and non-tuberculous mycobacteria.
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Cystic fibrosis (CF) is an autosomal recessive disease characterized
by pancreatic insufficiency and chronic endobronchial airway infection."
explanation: Clinical review identifies chronic endobronchial infection as a
defining characteristic of CF.
biological_processes:
- preferred_term: Defense response to bacterium
modifier: DYSREGULATED
term:
id: GO:0042742
label: defense response to bacterium
downstream:
- target: Neutrophilic Airway Inflammation
description: Chronic infection drives persistent neutrophil-predominant airway
inflammation.
evidence:
- reference: PMID:23878362
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "CF lungs are characterized by viscous, dehydrated mucus, persistent
neutrophilia and chronic infections. ENaC is negatively regulated by CFTR and,
in patients with CF, the absence of CFTR results in a double hit of reduced
Cl-/HCO3- and H2O secretion as well as ENaC hyperactivity and increased Na+
and H2O absorption."
explanation: Supports infection-associated persistent neutrophilia in CF
lungs.
- target: Bronchiectasis
description: Recurrent endobronchial infection contributes to progressive
bronchiectatic damage.
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "This latter feature results in progressive bronchiectasis and ultimately
respiratory failure, which is the leading cause of death in patients with CF."
explanation: Supports chronic airway infection as an upstream driver of
bronchiectasis.
- name: Neutrophilic Airway Inflammation
description: >-
The CF airway shows persistent neutrophil-predominant inflammation, with a
protease-rich inflammatory milieu that amplifies local tissue injury.
cell_types:
- preferred_term: Neutrophil
term:
id: CL:0000775
label: neutrophil
biological_processes:
- preferred_term: Inflammatory response
modifier: INCREASED
term:
id: GO:0006954
label: inflammatory response
- preferred_term: neutrophil chemotaxis
modifier: INCREASED
term:
id: GO:0030593
label: neutrophil chemotaxis
evidence:
- reference: PMID:29258516
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "The role of neutrophil elastase (NE) is poorly understood in bronchiectasis
because of the lack of preclinical data and so most of the assumptions made
about NE inhibitor potential benefit is based on data from CF."
explanation: Review confirms neutrophil elastase as a key marker of
inflammation in CF and bronchiectasis.
downstream:
- target: Neutrophil Elastase-Mediated Tissue Injury
description: Protease-dominant neutrophilic inflammation drives extracellular
airway tissue damage.
evidence:
- reference: PMID:29258516
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "The role of neutrophil elastase (NE) is poorly understood in bronchiectasis
because of the lack of preclinical data and so most of the assumptions made
about NE inhibitor potential benefit is based on data from CF."
explanation: Supports neutrophil elastase as a mechanistically relevant injury
effector derived from CF-related neutrophilic inflammation.
- name: Neutrophil Elastase-Mediated Tissue Injury
description: >-
Neutrophil elastase burden and protease-antiprotease imbalance contribute to
structural airway tissue damage.
biological_processes:
- preferred_term: proteolysis
modifier: INCREASED
term:
id: GO:0006508
label: proteolysis
evidence:
- reference: PMID:29258516
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "In this review sputum NE has proved useful as an inflammatory marker
both in stable state bronchiectasis and during exacerbations and local or systemic
antibiotic treatment."
explanation: Supports persistent NE activity as a biologically relevant marker
in chronic suppurative airway disease with CF-based mechanistic context.
downstream:
- target: Airway Remodeling
description: Persistent proteolytic injury promotes abnormal airway wall
remodeling.
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "This latter feature results in progressive bronchiectasis and ultimately
respiratory failure, which is the leading cause of death in patients with CF."
explanation: Supports progression from chronic airway injury to irreversible
structural disease.
- name: Airway Remodeling
description: >-
Repeated infection-inflammation injury cycles alter airway wall architecture,
producing thickening, scarring, and loss of normal elastic structure.
biological_processes:
- preferred_term: extracellular matrix organization
modifier: ABNORMAL
term:
id: GO:0030198
label: extracellular matrix organization
locations:
- preferred_term: Lung
term:
id: UBERON:0002048
label: lung
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "This latter feature results in progressive bronchiectasis and ultimately
respiratory failure, which is the leading cause of death in patients with CF."
explanation: Supports progressive structural airway deterioration in CF lung
disease.
downstream:
- target: Bronchiectasis
description: Structural remodeling culminates in irreversible bronchial dilation.
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "This latter feature results in progressive bronchiectasis and ultimately
respiratory failure, which is the leading cause of death in patients with CF."
explanation: Supports bronchiectasis as an endpoint of progressive airway
remodeling.
- name: Bronchiectasis
description: >-
Progressive, irreversible bronchial dilation develops from chronic obstruction,
infection, and inflammatory injury.
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "This latter feature results in progressive bronchiectasis and ultimately
respiratory failure, which is the leading cause of death in patients with CF."
explanation: Clinical review confirms progressive bronchiectasis leading to
respiratory failure as the primary cause of mortality.
locations:
- preferred_term: Lung
term:
id: UBERON:0002048
label: lung
downstream:
- target: Respiratory Failure
description: End-stage bronchiectasis leads to hypoxemic and hypercapnic
respiratory failure.
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "This latter feature results in progressive bronchiectasis and ultimately
respiratory failure, which is the leading cause of death in patients with CF."
explanation: Supports direct progression from advanced bronchiectasis to
respiratory failure.
- name: Respiratory Failure
description: >-
End-stage CF lung disease results in progressive respiratory failure with
hypoxemia, hypercapnia, and cor pulmonale. Respiratory failure is the leading
cause of death in CF patients and the primary indication for lung
transplantation.
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "This latter feature results in progressive bronchiectasis and ultimately
respiratory failure, which is the leading cause of death in patients with CF."
explanation: Respiratory failure is confirmed as the leading cause of CF
mortality.
- name: Pancreatic Duct Obstruction
description: >-
CFTR dysfunction in pancreatic ductal epithelium impairs bicarbonate and fluid
secretion, leading to viscid secretions that obstruct pancreatic ducts.
cell_types:
- preferred_term: Pancreatic ductal cell
term:
id: CL:0002079
label: pancreatic ductal cell
biological_processes:
- preferred_term: bicarbonate transport
modifier: DECREASED
term:
id: GO:0015701
label: bicarbonate transport
locations:
- preferred_term: Pancreas
term:
id: UBERON:0001264
label: pancreas
evidence:
- reference: PMID:33526571
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Clinical characteristics include progressive obstructive lung disease,
sinusitis, exocrine pancreatic insufficiency leading to malabsorption and malnutrition,
liver and pancreatic dysfunction, and male infertility."
explanation: Pediatric review confirms pancreatic insufficiency and
dysfunction as core CF manifestations.
downstream:
- target: Exocrine Pancreatic Tissue Destruction
description: Persistent ductal obstruction promotes acinar injury and fibrosis.
evidence:
- reference: PMID:33526571
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Clinical characteristics include progressive obstructive lung disease,
sinusitis, exocrine pancreatic insufficiency leading to malabsorption and malnutrition,
liver and pancreatic dysfunction, and male infertility."
explanation: Supports progression from pancreatic dysfunction to destructive
exocrine pancreatic disease.
- target: Exocrine Pancreatic Insufficiency
description: Ductal disease progresses to insufficient exocrine enzyme output.
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Cystic fibrosis (CF) is an autosomal recessive disease characterized
by pancreatic insufficiency and chronic endobronchial airway infection."
explanation: Supports pancreatic insufficiency as a major downstream endpoint
of pancreatic duct disease.
- name: Exocrine Pancreatic Tissue Destruction
description: >-
Ongoing duct obstruction and intrapancreatic injury damage exocrine tissue and
promote fibrosis.
cell_types:
- preferred_term: Pancreatic acinar cell
term:
id: CL:0002064
label: pancreatic acinar cell
biological_processes:
- preferred_term: proteolysis
modifier: INCREASED
term:
id: GO:0006508
label: proteolysis
locations:
- preferred_term: Pancreas
term:
id: UBERON:0001264
label: pancreas
evidence:
- reference: PMID:33526571
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Clinical characteristics include progressive obstructive lung disease,
sinusitis, exocrine pancreatic insufficiency leading to malabsorption and malnutrition,
liver and pancreatic dysfunction, and male infertility."
explanation: Supports destructive pancreatic dysfunction as part of the CF
multiorgan phenotype.
downstream:
- target: Exocrine Pancreatic Insufficiency
description: Loss of acinar tissue lowers digestive enzyme delivery to the gut.
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Cystic fibrosis (CF) is an autosomal recessive disease characterized
by pancreatic insufficiency and chronic endobronchial airway infection."
explanation: Supports exocrine insufficiency as a direct pancreatic outcome.
- target: CF-Related Diabetes
description: Progressive pancreatic destruction contributes to insulin deficiency.
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Other complications include sinusitis, diabetes mellitus, bowel obstruction,
hepatobiliary disease, hyponatremic dehydration, and infertility."
explanation: Supports diabetes mellitus as a downstream pancreatic complication
in CF.
- name: Exocrine Pancreatic Insufficiency
description: >-
Destruction of exocrine pancreatic tissue causes insufficient production of
digestive enzymes including lipase, amylase, and proteases. Present in 85-90%
of CF patients, pancreatic insufficiency causes fat and protein malabsorption
leading to steatorrhea, failure to thrive, and fat-soluble vitamin deficiency
(vitamins A, D, E, K). Pancreatic sufficiency is more common in patients with
at least one mild (class IV-V) CFTR mutation.
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Cystic fibrosis (CF) is an autosomal recessive disease characterized
by pancreatic insufficiency and chronic endobronchial airway infection."
explanation: Clinical review identifies pancreatic insufficiency as a
defining characteristic of cystic fibrosis.
downstream:
- target: Fat Malabsorption
description: Low pancreatic lipase causes fat malabsorption with
steatorrhea.
evidence:
- reference: PMID:33526571
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Clinical characteristics include progressive obstructive lung disease,
sinusitis, exocrine pancreatic insufficiency leading to malabsorption and malnutrition,
liver and pancreatic dysfunction, and male infertility."
explanation: Supports direct progression from exocrine pancreatic insufficiency
to malabsorption.
- target: Fat-Soluble Vitamin Deficiency
description: Malabsorption of vitamins A, D, E, K causes deficiency states.
evidence:
- reference: PMID:33526571
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Clinical characteristics include progressive obstructive lung disease,
sinusitis, exocrine pancreatic insufficiency leading to malabsorption and malnutrition,
liver and pancreatic dysfunction, and male infertility."
explanation: Supports vitamin deficiency risk as part of exocrine
insufficiency-driven malabsorption.
- target: Protein-Calorie Malnutrition
description: Impaired digestion and absorption lead to failure to thrive.
evidence:
- reference: PMID:33526571
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Clinical characteristics include progressive obstructive lung disease,
sinusitis, exocrine pancreatic insufficiency leading to malabsorption and malnutrition,
liver and pancreatic dysfunction, and male infertility."
explanation: Supports malnutrition as a direct nutritional consequence of
exocrine insufficiency.
- name: Fat Malabsorption
description: >-
Insufficient pancreatic lipase causes malabsorption of dietary fat, resulting
in
steatorrhea (fatty, bulky, foul-smelling stools), caloric loss, and deficiency
of fat-soluble vitamins. Fat malabsorption is a major contributor to
malnutrition and failure to thrive in CF.
biological_processes:
- preferred_term: lipid digestion
modifier: DECREASED
term:
id: GO:0044241
label: lipid digestion
evidence:
- reference: PMID:33526571
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Clinical characteristics include progressive obstructive lung disease,
sinusitis, exocrine pancreatic insufficiency leading to malabsorption and malnutrition,
liver and pancreatic dysfunction, and male infertility."
explanation: Pediatric review confirms malabsorption as a clinical
characteristic of CF.
downstream:
- target: Fat-Soluble Vitamin Deficiency
description: Impaired intestinal fat absorption reduces uptake of vitamins A, D, E, and K.
evidence:
- reference: PMID:33526571
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Clinical characteristics include progressive obstructive lung disease,
sinusitis, exocrine pancreatic insufficiency leading to malabsorption and malnutrition,
liver and pancreatic dysfunction, and male infertility."
explanation: Supports vitamin deficiency risk downstream of CF malabsorption.
- target: Protein-Calorie Malnutrition
description: Chronic caloric and nutrient loss worsens growth and nutritional status.
evidence:
- reference: PMID:33178516
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "It classically presents in childhood with chronic productive cough,
malabsorption causing steatorrhea, and failure to thrive."
explanation: Supports progression from malabsorption to failure-to-thrive
malnutrition phenotype.
- name: Fat-Soluble Vitamin Deficiency
description: >-
Malabsorption of fat-soluble vitamins A, D, E, and K leads to specific
deficiency states. Vitamin A deficiency can cause night blindness, vitamin D
deficiency contributes to CF bone disease, vitamin E deficiency may cause
neurological symptoms, and vitamin K deficiency increases bleeding risk.
evidence:
- reference: PMID:33526571
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Clinical characteristics include progressive obstructive lung disease,
sinusitis, exocrine pancreatic insufficiency leading to malabsorption and malnutrition,
liver and pancreatic dysfunction, and male infertility."
explanation: Malabsorption leads to vitamin deficiencies as part of the CF
nutritional phenotype.
downstream:
- target: CF Bone Disease
description: Chronic vitamin D and K deficiency contributes to low bone mass
and skeletal fragility.
evidence:
- reference: PMID:33526571
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Clinical characteristics include progressive obstructive lung disease,
sinusitis, exocrine pancreatic insufficiency leading to malabsorption and malnutrition,
liver and pancreatic dysfunction, and male infertility."
explanation: Supports malabsorption-driven nutritional pathology as an
upstream contributor to CF bone disease.
- name: Protein-Calorie Malnutrition
description: >-
Combined effects of pancreatic insufficiency, increased metabolic demands from
chronic infection and inflammation, and poor appetite lead to protein-calorie
malnutrition, failure to thrive in children, and poor weight maintenance in
adults. Nutritional status is strongly correlated with lung function and survival.
evidence:
- reference: PMID:33178516
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "It classically presents in childhood with chronic productive cough,
malabsorption causing steatorrhea, and failure to thrive."
explanation: Case report review confirms malabsorption and failure to thrive
as classic CF presentations.
downstream:
- target: CF Bone Disease
description: Sustained undernutrition worsens bone accrual and skeletal strength.
evidence:
- reference: PMID:33526571
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Clinical characteristics include progressive obstructive lung disease,
sinusitis, exocrine pancreatic insufficiency leading to malabsorption and malnutrition,
liver and pancreatic dysfunction, and male infertility."
explanation: Supports chronic malnutrition as a plausible upstream contributor
to CF bone disease.
- name: CF-Related Diabetes
description: >-
Progressive fibrosis and fatty infiltration of the pancreas destroys
islets of Langerhans, reducing insulin secretion capacity. CF-related diabetes
(CFRD) is distinct from type 1 and type 2 diabetes, characterized primarily by
insulin insufficiency with variable insulin resistance, especially during
pulmonary exacerbations. CFRD affects up to 50% of adult CF patients and is
associated with accelerated decline in lung function and increased mortality
if untreated.
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Other complications include sinusitis, diabetes mellitus, bowel obstruction,
hepatobiliary disease, hyponatremic dehydration, and infertility."
explanation: Clinical review lists diabetes mellitus among established
complications of CF.
cell_types:
- preferred_term: Pancreatic beta cell
term:
id: CL:0000169
label: type B pancreatic cell
locations:
- preferred_term: Pancreas
term:
id: UBERON:0001264
label: pancreas
- name: Intestinal Obstruction
description: >-
Dehydrated intestinal secretions cause bowel obstruction at different ages.
Meconium ileus occurs in 15-20% of CF neonates due to inspissated meconium
in the distal ileum. In older children and adults, distal intestinal
obstruction syndrome (DIOS) presents with similar pathophysiology in the
ileocecal region. Constipation is also common due to dehydrated intestinal
contents.
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Other complications include sinusitis, diabetes mellitus, bowel obstruction,
hepatobiliary disease, hyponatremic dehydration, and infertility."
explanation: Clinical review lists bowel obstruction among established
complications of CF.
- name: Hepatobiliary Obstruction
description: >-
CFTR dysfunction in cholangiocytes causes viscid bile secretions that obstruct
intrahepatic bile ductules. This leads to focal biliary cirrhosis, which can
progress to multilobular cirrhosis with portal hypertension in 5-10% of CF
patients. CF liver disease is the third leading cause of death after
respiratory failure and transplant complications.
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Other complications include sinusitis, diabetes mellitus, bowel obstruction,
hepatobiliary disease, hyponatremic dehydration, and infertility."
explanation: Clinical review lists hepatobiliary disease among established
complications of CF.
cell_types:
- preferred_term: Cholangiocyte
term:
id: CL:1000488
label: cholangiocyte
locations:
- preferred_term: Liver
term:
id: UBERON:0002107
label: liver
- name: Sweat Gland Dysfunction
description: >-
In sweat glands, CFTR is required for chloride reabsorption in the sweat duct.
Loss of CFTR function results in failure to reabsorb chloride from primary sweat,
producing sweat with elevated chloride concentration. This is the basis of the
diagnostic sweat chloride test. Excessive salt loss can cause hyponatremic
dehydration, especially in hot weather or during exercise.
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Diagnosis of CF is confirmed by demonstration of elevated sweat chloride."
explanation: Elevated sweat chloride reflects defective CFTR-mediated
chloride reabsorption in sweat ducts.
biological_processes:
- preferred_term: Chloride Transport
modifier: DECREASED
term:
id: GO:0006821
label: chloride transport
downstream:
- target: Hyponatremic Dehydration
description: Chronic sweat salt loss predisposes to hyponatremic volume depletion.
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Other complications include sinusitis, diabetes mellitus, bowel obstruction,
hepatobiliary disease, hyponatremic dehydration, and infertility."
explanation: Supports hyponatremic dehydration as a direct downstream
consequence of sweat-gland salt-loss physiology.
- name: Hyponatremic Dehydration
description: >-
Excessive sweat sodium and chloride loss can produce clinically significant
hyponatremic dehydration, especially with heat stress or inadequate salt intake.
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Other complications include sinusitis, diabetes mellitus, bowel obstruction,
hepatobiliary disease, hyponatremic dehydration, and infertility."
explanation: Clinical review lists hyponatremic dehydration among established
cystic fibrosis complications.
- name: Vas Deferens Agenesis
description: >-
CFTR is required for normal development of the Wolffian duct derivatives.
Congenital bilateral absence of the vas deferens (CBAVD) occurs in approximately
97-98% of males with CF due to inspissation and atresia of the vas deferens
during fetal development. CBAVD causes obstructive azoospermia and male
infertility. Notably, CBAVD can occur as an isolated finding in males who
carry one or two CFTR mutations with residual function, representing a
CFTR-related disorder.
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Other complications include sinusitis, diabetes mellitus, bowel obstruction,
hepatobiliary disease, hyponatremic dehydration, and infertility."
explanation: Clinical review confirms infertility as an established
complication of CF.
- name: Sinonasal Disease
description: >-
CFTR dysfunction in the sinonasal epithelium causes mucus retention and chronic
inflammation in the paranasal sinuses. Chronic rhinosinusitis affects nearly all
CF patients. Nasal polyposis occurs in 10-32% of CF patients and is unusual in
children without CF, making it an important diagnostic clue.
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Other complications include sinusitis, diabetes mellitus, bowel obstruction,
hepatobiliary disease, hyponatremic dehydration, and infertility."
explanation: Clinical review lists sinusitis among established complications
of CF.
- name: CF Bone Disease
description: >-
CF-related bone disease results from multiple converging mechanisms including
vitamin D deficiency from fat malabsorption, chronic systemic inflammation
with elevated cytokines (IL-6, TNF-alpha) that promote osteoclast activity,
reduced physical activity, delayed puberty with reduced sex steroids,
glucocorticoid use, and possibly direct CFTR effects on osteoblast function.
Osteopenia and osteoporosis are common in adults with CF.
evidence:
- reference: PMID:33526571
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Clinical characteristics include progressive obstructive lung disease,
sinusitis, exocrine pancreatic insufficiency leading to malabsorption and malnutrition,
liver and pancreatic dysfunction, and male infertility."
explanation: Malnutrition from pancreatic insufficiency contributes to bone
disease in CF patients.
phenotypes:
# Respiratory phenotypes
- category: Respiratory
name: Chronic Productive Cough
description: Persistent cough with purulent sputum production, often the
earliest respiratory symptom of CF.
frequency: VERY_FREQUENT
diagnostic: true
notes: One of the classic presenting symptoms of CF along with steatorrhea and
failure to thrive.
phenotype_term:
preferred_term: Chronic Productive Cough
term:
id: HP:0031245
label: Productive cough
evidence:
- reference: PMID:33178516
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "It classically presents in childhood with chronic productive cough,
malabsorption causing steatorrhea, and failure to thrive."
explanation: Review confirms chronic productive cough as a classic
presentation of cystic fibrosis.
- category: Respiratory
name: Recurrent Respiratory Infections
description: Chronic and recurrent lower respiratory tract infections with
characteristic CF pathogens including Pseudomonas aeruginosa and
Staphylococcus aureus.
frequency: VERY_FREQUENT
diagnostic: true
notes: Chronic Pseudomonas aeruginosa and Staphylococcus aureus infections are
hallmarks of CF lung disease.
phenotype_term:
preferred_term: Recurrent Respiratory Infections
term:
id: HP:0002205
label: Recurrent respiratory infections
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Cystic fibrosis (CF) is an autosomal recessive disease characterized
by pancreatic insufficiency and chronic endobronchial airway infection."
explanation: Clinical review identifies chronic airway infection as a
defining characteristic of cystic fibrosis.
- category: Respiratory
name: Bronchiectasis
description: Progressive airway damage from chronic infection and inflammation
leading to permanent bronchial dilation.
frequency: VERY_FREQUENT
notes: Progressive and eventually universal in CF patients; the primary driver
of morbidity and mortality.
phenotype_term:
preferred_term: Bronchiectasis
term:
id: HP:0002110
label: Bronchiectasis
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "This latter feature results in progressive bronchiectasis and ultimately
respiratory failure, which is the leading cause of death in patients with CF."
explanation: Clinical review confirms progressive bronchiectasis as a
consequence of chronic airway infection in CF.
- category: Respiratory
name: Hemoptysis
description: Coughing up blood due to erosion of bronchial arteries by chronic
inflammation and bronchiectasis. Massive hemoptysis (>240 mL/day) is a
life-threatening complication requiring bronchial artery embolization.
frequency: FREQUENT
notes: Minor hemoptysis is common; massive hemoptysis occurs in 4-5% of
patients.
phenotype_term:
preferred_term: Hemoptysis
term:
id: HP:0002105
label: Hemoptysis
evidence:
- reference: PMID:33526571
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Clinical characteristics include progressive obstructive lung disease,
sinusitis, exocrine pancreatic insufficiency leading to malabsorption and malnutrition,
liver and pancreatic dysfunction, and male infertility."
explanation: Progressive obstructive lung disease leads to complications
including hemoptysis.
- category: Respiratory
name: Pneumothorax
description: Spontaneous pneumothorax from rupture of subpleural blebs,
occurring in patients with advanced lung disease. Risk increases with
severity of airflow obstruction.
frequency: OCCASIONAL
notes: Occurs in 3-4% of CF patients; recurrence rate is high.
phenotype_term:
preferred_term: Pneumothorax
term:
id: HP:0002107
label: Pneumothorax
evidence:
- reference: PMID:33526571
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Clinical characteristics include progressive obstructive lung disease,
sinusitis, exocrine pancreatic insufficiency leading to malabsorption and malnutrition,
liver and pancreatic dysfunction, and male infertility."
explanation: Progressive obstructive lung disease is associated with
complications such as pneumothorax.
- category: Respiratory
name: Allergic Bronchopulmonary Aspergillosis
description: Hypersensitivity response to Aspergillus fumigatus colonization
of CF airways, causing worsening airflow obstruction, mucus plugging, and
central bronchiectasis.
frequency: OCCASIONAL
notes: Affects 2-15% of CF patients; requires high index of suspicion.
evidence:
- reference: PMID:33526571
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Clinical characteristics include progressive obstructive lung disease,
sinusitis, exocrine pancreatic insufficiency leading to malabsorption and malnutrition,
liver and pancreatic dysfunction, and male infertility."
explanation: Progressive obstructive lung disease encompasses various
complications including fungal sensitization.
- category: Respiratory
name: Digital Clubbing
description: Enlargement and rounding of the fingertips and nail beds due to
chronic hypoxemia from progressive lung disease.
frequency: FREQUENT
notes: Develops with progression of lung disease; correlates with severity.
phenotype_term:
preferred_term: Digital Clubbing
term:
id: HP:0001217
label: Clubbing
evidence:
- reference: PMID:33526571
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Clinical characteristics include progressive obstructive lung disease,
sinusitis, exocrine pancreatic insufficiency leading to malabsorption and malnutrition,
liver and pancreatic dysfunction, and male infertility."
explanation: Progressive obstructive lung disease leads to chronic hypoxemia
and clubbing.
# ENT phenotypes
- category: ENT
name: Nasal Polyposis
description: Benign mucosal growths in the nasal passages and paranasal
sinuses. Nasal polyposis in children is highly suggestive of CF and should
prompt diagnostic evaluation.
frequency: FREQUENT
notes: Present in 10-32% of CF patients. In children, nasal polyps are
uncommon outside of CF and should trigger sweat testing.
phenotype_term:
preferred_term: Nasal Polyposis
term:
id: HP:0100582
label: Nasal polyposis
- category: ENT
name: Chronic Sinusitis
description: Near-universal chronic rhinosinusitis in CF patients due to mucus
retention and inflammation in the paranasal sinuses. Often causes nasal
obstruction, facial pain, and anosmia.
frequency: VERY_FREQUENT
notes: Radiographic sinusitis is nearly universal; symptomatic disease varies.
phenotype_term:
preferred_term: Chronic Sinusitis
term:
id: HP:0011109
label: Chronic sinusitis
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Other complications include sinusitis, diabetes mellitus, bowel obstruction,
hepatobiliary disease, hyponatremic dehydration, and infertility."
explanation: Clinical review lists sinusitis among established complications
of CF.
# Gastrointestinal phenotypes
- category: Gastrointestinal
name: Exocrine Pancreatic Insufficiency
description: Insufficient production of pancreatic digestive enzymes causing
malabsorption of fats, proteins, and fat-soluble vitamins.
frequency: VERY_FREQUENT
diagnostic: true
notes: Present in 85-90% of CF patients, typically those with two severe CFTR
mutations. Patients with at least one mild mutation may retain pancreatic
sufficiency.
phenotype_term:
preferred_term: Pancreatic Insufficiency
term:
id: HP:0001738
label: Exocrine pancreatic insufficiency
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Cystic fibrosis (CF) is an autosomal recessive disease characterized
by pancreatic insufficiency and chronic endobronchial airway infection."
explanation: Clinical review identifies pancreatic insufficiency as a
defining characteristic of cystic fibrosis.
- category: Gastrointestinal
name: Steatorrhea
description: Fatty, bulky, foul-smelling stools resulting from fat
malabsorption due to pancreatic lipase deficiency.
frequency: VERY_FREQUENT
notes: A classic presenting symptom of CF in infancy and early childhood.
phenotype_term:
preferred_term: Steatorrhea
term:
id: HP:0002570
label: Steatorrhea
evidence:
- reference: PMID:33178516
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "It classically presents in childhood with chronic productive cough,
malabsorption causing steatorrhea, and failure to thrive."
explanation: Review confirms steatorrhea as a classic presentation of cystic
fibrosis due to malabsorption.
- category: Gastrointestinal
name: Meconium Ileus
description: Neonatal bowel obstruction caused by inspissated meconium in the
distal ileum, often the first clinical manifestation of CF.
frequency: OCCASIONAL
diagnostic: true
notes: Present in 15-20% of CF newborns. May be complicated by volvulus,
atresia, or perforation. Meconium ileus in a neonate is highly suggestive of
CF.
phenotype_term:
preferred_term: Meconium Ileus
term:
id: HP:0004401
label: Meconium ileus
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Other complications include sinusitis, diabetes mellitus, bowel obstruction,
hepatobiliary disease, hyponatremic dehydration, and infertility."
explanation: Clinical review lists bowel obstruction (including meconium
ileus) among established complications of CF.
- category: Gastrointestinal
name: Distal Intestinal Obstruction Syndrome
description: Partial or complete intestinal obstruction in the ileocecal
region due to accumulation of viscid intestinal contents. Analogous to
meconium ileus but occurring in older children and adults.
frequency: OCCASIONAL
notes: Occurs in approximately 10-15% of CF patients. Risk factors include
pancreatic insufficiency, dehydration, and inadequate enzyme replacement.
phenotype_term:
preferred_term: Intestinal Obstruction
term:
id: HP:0005214
label: Intestinal obstruction
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Other complications include sinusitis, diabetes mellitus, bowel obstruction,
hepatobiliary disease, hyponatremic dehydration, and infertility."
explanation: Bowel obstruction including DIOS is an established complication
in CF patients.
- category: Gastrointestinal
name: Rectal Prolapse
description: Protrusion of rectal mucosa through the anus, historically a
common presenting feature of CF in undiagnosed children due to malnutrition
and chronic cough-related straining.
frequency: OCCASIONAL
notes: Less common since advent of newborn screening and early treatment.
phenotype_term:
preferred_term: Rectal Prolapse
term:
id: HP:0002035
label: Rectal prolapse
evidence:
- reference: PMID:33526571
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Clinical characteristics include progressive obstructive lung disease,
sinusitis, exocrine pancreatic insufficiency leading to malabsorption and malnutrition,
liver and pancreatic dysfunction, and male infertility."
explanation: Malnutrition from pancreatic insufficiency contributes to
complications like rectal prolapse.
- category: Gastrointestinal
name: Gastroesophageal Reflux
description: Increased gastroesophageal reflux in CF patients, potentially
exacerbated by cough, chest physiotherapy, and increased abdominal pressure.
May worsen lung disease through aspiration.
frequency: FREQUENT
phenotype_term:
preferred_term: Gastroesophageal Reflux
term:
id: HP:0002020
label: Gastroesophageal reflux
evidence:
- reference: PMID:33526571
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Clinical characteristics include progressive obstructive lung disease,
sinusitis, exocrine pancreatic insufficiency leading to malabsorption and malnutrition,
liver and pancreatic dysfunction, and male infertility."
explanation: GI complications are common in CF and include gastroesophageal
reflux.
# Hepatobiliary phenotypes
- category: Hepatobiliary
name: Focal Biliary Cirrhosis
description: Obstruction of intrahepatic bile ductules by viscid secretions
causes focal biliary fibrosis, which may progress to multilobular cirrhosis
with portal hypertension in 5-10% of patients.
frequency: OCCASIONAL
notes: CF liver disease is the third leading cause of CF mortality.
Ursodeoxycholic acid may slow progression.
phenotype_term:
preferred_term: Biliary Cirrhosis
term:
id: HP:0002613
label: Biliary cirrhosis
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Other complications include sinusitis, diabetes mellitus, bowel obstruction,
hepatobiliary disease, hyponatremic dehydration, and infertility."
explanation: Clinical review lists hepatobiliary disease among established
complications of CF.
- category: Hepatobiliary
name: Portal Hypertension
description: Increased portal venous pressure from multilobular biliary
cirrhosis, which may cause variceal bleeding, splenomegaly, and ascites.
frequency: OCCASIONAL
notes: Occurs in patients who progress to multilobular cirrhosis. May require
portosystemic shunting or liver transplantation.
phenotype_term:
preferred_term: Portal Hypertension
term:
id: HP:0001409
label: Portal hypertension
evidence:
- reference: PMID:33526571
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Clinical characteristics include progressive obstructive lung disease,
sinusitis, exocrine pancreatic insufficiency leading to malabsorption and malnutrition,
liver and pancreatic dysfunction, and male infertility."
explanation: Liver and pancreatic dysfunction in CF includes cirrhosis
leading to portal hypertension.
# Endocrine phenotypes
- category: Endocrine
name: CF-Related Diabetes
description: Diabetes caused by progressive destruction of pancreatic islets,
characterized by insulin insufficiency with variable insulin resistance.
Distinct from type 1 and type 2 diabetes. Associated with accelerated
decline in lung function and increased mortality if untreated.
frequency: FREQUENT
notes: Prevalence increases with age, affecting up to 20% of adolescents and
50% of adults with CF. Annual screening with oral glucose tolerance test
recommended from age 10.
phenotype_term:
preferred_term: Diabetes Mellitus
term:
id: HP:0000819
label: Diabetes mellitus
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Other complications include sinusitis, diabetes mellitus, bowel obstruction,
hepatobiliary disease, hyponatremic dehydration, and infertility."
explanation: Clinical review lists diabetes mellitus among established
complications of CF.
- category: Endocrine
name: Delayed Puberty
description: Delayed onset of puberty due to chronic illness, malnutrition,
and possibly direct effects of CFTR dysfunction on gonadal function.
frequency: FREQUENT
notes: More common when nutritional status is poor.
phenotype_term:
preferred_term: Delayed Puberty
term:
id: HP:0000823
label: Delayed puberty
evidence:
- reference: PMID:33526571
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Clinical characteristics include progressive obstructive lung disease,
sinusitis, exocrine pancreatic insufficiency leading to malabsorption and malnutrition,
liver and pancreatic dysfunction, and male infertility."
explanation: Malnutrition from pancreatic insufficiency contributes to
delayed puberty in CF patients.
# Growth phenotypes
- category: Growth
name: Failure to Thrive
description: Poor weight gain and growth failure due to pancreatic
insufficiency, malabsorption, increased caloric requirements from chronic
lung infection, and poor appetite.
frequency: VERY_FREQUENT
diagnostic: true
notes: A classic presenting feature, especially before newborn screening era.
Nutritional status strongly correlates with lung function and survival.
phenotype_term:
preferred_term: Failure to Thrive
term:
id: HP:0001508
label: Failure to thrive
evidence:
- reference: PMID:33178516
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "It classically presents in childhood with chronic productive cough,
malabsorption causing steatorrhea, and failure to thrive."
explanation: Review confirms failure to thrive as a classic presentation of
cystic fibrosis.
- category: Growth
name: Short Stature
description: Reduced height for age resulting from chronic malnutrition,
systemic inflammation, and delayed puberty.
frequency: FREQUENT
notes: Improved with optimized nutritional support and CFTR modulator therapy.
phenotype_term:
preferred_term: Short Stature
term:
id: HP:0004322
label: Short stature
evidence:
- reference: PMID:33526571
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Clinical characteristics include progressive obstructive lung disease,
sinusitis, exocrine pancreatic insufficiency leading to malabsorption and malnutrition,
liver and pancreatic dysfunction, and male infertility."
explanation: Malnutrition from pancreatic insufficiency contributes to
growth failure and short stature.
# Reproductive phenotypes
- category: Reproductive
name: Male Infertility
description: Obstructive azoospermia due to congenital bilateral absence of
the vas deferens (CBAVD) in 97-98% of males with CF. Spermatogenesis is
usually normal, and assisted reproduction is possible via sperm extraction
techniques.
frequency: VERY_FREQUENT
diagnostic: true
notes: CBAVD can also occur as an isolated finding in males carrying one or
two CFTR mutations, representing a CFTR-related disorder.
phenotype_term:
preferred_term: Male Infertility
term:
id: HP:0003251
label: Male infertility
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Other complications include sinusitis, diabetes mellitus, bowel obstruction,
hepatobiliary disease, hyponatremic dehydration, and infertility."
explanation: Clinical review lists infertility among the established
complications of cystic fibrosis.
- category: Reproductive
name: Reduced Female Fertility
description: Reduced fertility in females with CF due to thick cervical mucus
that impairs sperm transport. Fertility is improved with CFTR modulator
therapy and nutritional optimization.
frequency: FREQUENT
notes: Not absolute infertility; many CF women conceive, especially with
improved health status on modulator therapy.
phenotype_term:
preferred_term: Reduced Female Fertility
term:
id: HP:0008222
label: Female infertility
evidence:
- reference: PMID:33526571
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Clinical characteristics include progressive obstructive lung disease,
sinusitis, exocrine pancreatic insufficiency leading to malabsorption and malnutrition,
liver and pancreatic dysfunction, and male infertility."
explanation: Reproductive complications including reduced fertility affect
CF patients.
# Metabolic phenotypes
- category: Metabolic
name: Hyponatremic Dehydration
description: Excessive sodium and chloride loss in sweat predisposes CF
patients to salt-depletion dehydration, especially in hot weather, during
exercise, or with gastroenteritis.
frequency: OCCASIONAL
notes: Can be a presenting feature in infancy. Salt supplementation is
recommended.
phenotype_term:
preferred_term: Hyponatremia
term:
id: HP:0002902
label: Hyponatremia
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Other complications include sinusitis, diabetes mellitus, bowel obstruction,
hepatobiliary disease, hyponatremic dehydration, and infertility."
explanation: Clinical review lists hyponatremic dehydration among
established complications of CF.
- category: Metabolic
name: Fat-Soluble Vitamin Deficiency
description: Deficiency of vitamins A, D, E, and K due to fat malabsorption
from pancreatic insufficiency. Vitamin D deficiency contributes to bone
disease; vitamin K deficiency increases bleeding risk.
frequency: VERY_FREQUENT
notes: Routine supplementation of fat-soluble vitamins is standard of care.
phenotype_term:
preferred_term: Intestinal malabsorption
term:
id: HP:0002024
label: Malabsorption
evidence:
- reference: PMID:33526571
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Clinical characteristics include progressive obstructive lung disease,
sinusitis, exocrine pancreatic insufficiency leading to malabsorption and malnutrition,
liver and pancreatic dysfunction, and male infertility."
explanation: Malabsorption from pancreatic insufficiency causes vitamin
deficiencies.
# Musculoskeletal phenotypes
- category: Musculoskeletal
name: Osteoporosis
description: Reduced bone mineral density resulting from vitamin D deficiency,
chronic inflammation, reduced physical activity, delayed puberty, and
glucocorticoid exposure. Fracture risk is increased, particularly vertebral
and rib fractures.
frequency: FREQUENT
notes: Bone density screening with DXA recommended for adults with CF.
phenotype_term:
preferred_term: Osteoporosis
term:
id: HP:0000939
label: Osteoporosis
evidence:
- reference: PMID:33526571
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Clinical characteristics include progressive obstructive lung disease,
sinusitis, exocrine pancreatic insufficiency leading to malabsorption and malnutrition,
liver and pancreatic dysfunction, and male infertility."
explanation: Malnutrition and vitamin D deficiency from malabsorption
contribute to osteoporosis.
biochemical:
- name: Sweat Chloride
presence: Elevated
context: Sweat chloride >=60 mmol/L is diagnostic of CF; 30-59 mmol/L is
intermediate and requires further evaluation; <30 mmol/L makes CF unlikely.
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Diagnosis of CF is confirmed by demonstration of elevated sweat chloride."
explanation: Elevated sweat chloride is the diagnostic hallmark of CF.
- reference: PMID:28129811
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "It is recommended that diagnoses associated with CFTR mutations in all
individuals, from newborn to adult, be established by evaluation of CFTR function
with a sweat chloride test."
explanation: CF Foundation consensus guidelines recommend sweat chloride
testing for all CFTR-related diagnoses.
- name: Immunoreactive Trypsinogen (IRT)
presence: Elevated
context: Elevated in newborn dried blood spots; used as first-tier newborn
screening test. Elevated IRT reflects pancreatic injury in utero.
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Most cases of CF are identified through newborn screening (NBS)."
explanation: Newborn screening using IRT is the primary method of CF
identification.
- name: Fecal Elastase
presence: Decreased
context: Fecal elastase-1 <200 mcg/g indicates pancreatic insufficiency; <100
mcg/g indicates severe insufficiency. Used to confirm exocrine pancreatic
function status.
evidence:
- reference: PMID:33526571
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Clinical characteristics include progressive obstructive lung disease,
sinusitis, exocrine pancreatic insufficiency leading to malabsorption and malnutrition,
liver and pancreatic dysfunction, and male infertility."
explanation: Pancreatic insufficiency is assessed using fecal elastase
measurements.
- name: Fat-Soluble Vitamins (A, D, E, K)
presence: Decreased
context: Deficiencies common due to fat malabsorption in
pancreatic-insufficient patients. Levels should be monitored annually.
evidence:
- reference: PMID:33526571
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Clinical characteristics include progressive obstructive lung disease,
sinusitis, exocrine pancreatic insufficiency leading to malabsorption and malnutrition,
liver and pancreatic dysfunction, and male infertility."
explanation: Malabsorption from pancreatic insufficiency causes fat-soluble
vitamin deficiencies.
- name: Liver Enzymes
presence: Variable
context: Elevated ALT, AST, and GGT may indicate CF liver disease. GGT is
often the first to elevate.
evidence:
- reference: PMID:33526571
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Clinical characteristics include progressive obstructive lung disease,
sinusitis, exocrine pancreatic insufficiency leading to malabsorption and malnutrition,
liver and pancreatic dysfunction, and male infertility."
explanation: Liver dysfunction in CF is monitored using liver enzyme
measurements.
- name: Blood Glucose / HbA1c
presence: Variable
context: Annual oral glucose tolerance test recommended from age 10 for CFRD
screening. HbA1c is unreliable in CF due to increased red cell turnover.
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Other complications include sinusitis, diabetes mellitus, bowel obstruction,
hepatobiliary disease, hyponatremic dehydration, and infertility."
explanation: CF-related diabetes requires monitoring of glucose levels.
- name: Sputum Microbiology
presence: Variable
context: Routine sputum cultures guide antibiotic therapy. Typical organisms
include Staphylococcus aureus, Pseudomonas aeruginosa, Burkholderia cepacia
complex, and non-tuberculous mycobacteria.
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Cystic fibrosis (CF) is an autosomal recessive disease characterized
by pancreatic insufficiency and chronic endobronchial airway infection."
explanation: Chronic endobronchial infection is monitored through sputum
microbiology.
genetic:
- name: CFTR
association: Causative
notes: >-
The CFTR gene (7q31.2) encodes the cystic fibrosis transmembrane conductance
regulator, a 1480-amino acid chloride and bicarbonate channel. Nearly 2,000
CFTR variants have been identified. The Clinical and Functional Translation of
CFTR (CFTR2) project has systematically characterized disease liability of the
most common variants, with 159 variants at allele frequency >=0.01%, of which
127 met both clinical and functional criteria for disease causation.
evidence:
- reference: PMID:31697873
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Cystic fibrosis is caused by mutations in the gene encoding the cystic
fibrosis transmembrane conductance regulator (CFTR) protein, and nearly 90%
of patients have at least one copy of the Phe508del CFTR mutation."
explanation: Phase 3 trial confirms CFTR mutations cause CF and F508del is
the most common mutation.
- reference: PMID:23974870
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Few of the almost 2,000 variants in the cystic fibrosis transmembrane
conductance regulator gene CFTR have empirical evidence that they cause cystic
fibrosis."
explanation: CFTR2 project establishes the scope of CFTR variant
heterogeneity.
- reference: PMID:23974870
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "we collected both genotype and phenotype data for 39,696 individuals
with cystic fibrosis in registries and clinics in North America and Europe"
explanation: CFTR2 project provides the largest systematic analysis of CFTR
variant-disease relationships.
variants:
- name: F508del (Phe508del)
description: >-
Deletion of phenylalanine at position 508 in the CFTR protein. The most common
CF-causing mutation, present on at least one allele in nearly 90% of CF
patients. Causes misfolding of CFTR protein leading to endoplasmic reticulum
retention, proteasomal degradation, and near-complete absence of CFTR at the
cell surface (Class II defect). The small amount of protein reaching the
surface also has reduced channel open probability (Class III) and reduced
stability (Class VI).
evidence:
- reference: PMID:31697873
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "nearly 90% of patients have at least one copy of the Phe508del CFTR
mutation"
explanation: Confirms F508del is present in nearly 90% of CF patients.
- name: G551D (Gly551Asp)
description: >-
Missense mutation causing glycine-to-aspartate substitution at position 551.
CFTR protein reaches the cell surface normally but has severely reduced channel
gating (Class III defect). The first CFTR mutation for which targeted modulator
therapy (ivacaftor) was approved, producing dramatic clinical benefit.
evidence:
- reference: PMID:22047557
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "The change from baseline through week 24 in the percent of predicted
FEV(1) was greater by 10.6 percentage points in the ivacaftor group than in
the placebo group (P<0.001)."
explanation: Landmark Phase 3 trial demonstrating ivacaftor efficacy in
G551D patients.
- name: G542X
description: >-
Nonsense mutation creating a premature stop codon at position 542. No functional
CFTR protein is produced (Class I defect). One of the most common severe
mutations after F508del.
evidence:
- reference: PMID:23974870
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "These variants were evaluated for both clinical severity and functional
consequence, with 127 (80%) meeting both clinical and functional criteria
consistent with disease."
explanation: CFTR2 project establishes disease liability of common CFTR
variants including nonsense mutations.
- name: W1282X
description: >-
Nonsense mutation at position 1282 causing premature termination. Class I defect
with no functional protein produced. Common in Ashkenazi Jewish populations.
evidence:
- reference: PMID:23974870
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "These variants were evaluated for both clinical severity and functional
consequence, with 127 (80%) meeting both clinical and functional criteria
consistent with disease."
explanation: CFTR2 project classifies W1282X as a disease-causing variant.
- name: N1303K
description: >-
Missense mutation causing protein misfolding and degradation similar to F508del
(Class II defect).
evidence:
- reference: PMID:23974870
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "These variants were evaluated for both clinical severity and functional
consequence, with 127 (80%) meeting both clinical and functional criteria
consistent with disease."
explanation: CFTR2 project evaluates N1303K as a disease-causing variant.
- name: R117H
description: >-
Missense mutation producing CFTR with reduced chloride conductance (Class IV
defect). Associated with variable phenotype depending on the polythymidine
tract variant (5T, 7T, 9T) on the same allele. R117H-5T causes more severe
disease; R117H-7T may cause CFTR-related disorder or be benign.
diagnosis:
- name: Sweat Chloride Test (Quantitative Pilocarpine Iontophoresis)
description: >-
Gold standard diagnostic test for CF. Pilocarpine iontophoresis stimulates
localized sweating; sweat is collected and chloride concentration measured.
Chloride >=60 mmol/L is diagnostic, 30-59 mmol/L is intermediate, <30 mmol/L
is CF-unlikely.
diagnosis_term:
preferred_term: sweat electrolyte test
term:
id: MAXO:0035108
label: sweat electrolyte test
notes: Must be performed at a CF Foundation-accredited laboratory. Minimum
sweat volume required for reliable results. Should be performed on two
separate occasions.
evidence:
- reference: PMID:28576637
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Even in 2016, the most reliable and widely available diagnostic test
for CF is the measurement of chloride concentration in sweat."
explanation: Review emphasizes sweat chloride as the most reliable and
widely available diagnostic test.
- reference: PMID:28576637
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "The method of choice is sweat induction by pilocarpine iontophoresis,
followed by sweat collection on a gauze or filter paper or in a Macroduct coil."
explanation: Supports quantitative pilocarpine iontophoresis as the preferred
sweat testing approach.
- reference: PMID:28129811
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "It is recommended that diagnoses associated with CFTR mutations in all
individuals, from newborn to adult, be established by evaluation of CFTR function
with a sweat chloride test."
explanation: CF Foundation consensus guidelines establish sweat chloride as
the recommended diagnostic test.
- name: CFTR Genetic Testing
description: >-
Identification of two disease-causing CFTR mutations confirms the diagnosis.
Panel testing covers the most common mutations; expanded sequencing and
deletion/duplication analysis can identify rare variants. The CFTR2 database
provides clinical classification of variants.
diagnosis_term:
preferred_term: molecular genetic testing
term:
id: MAXO:0000533
label: molecular genetic testing
notes: Genetic testing alone is insufficient for diagnosis if sweat chloride
is normal, as some variants have variable penetrance.
evidence:
- reference: PMID:28855057
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Cystic fibrosis is caused by a gene mutation leading to dysfunction of
the cystic fibrosis transmembrane conductance regulator (CFTR) protein."
explanation: Supports the role of identifying disease-causing CFTR mutations
within a multimodal diagnostic framework.
- reference: PMID:23974870
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "These variants were evaluated for both clinical severity and functional
consequence, with 127 (80%) meeting both clinical and functional criteria consistent
with disease."
explanation: CFTR2 project provides systematic classification of CFTR
variants for diagnostic interpretation.
- name: Newborn Screening
description: >-
Population-based screening using immunoreactive trypsinogen (IRT) measured in
dried blood spots collected at 24-48 hours of life. Elevated IRT is followed by
either CFTR mutation panel or second IRT measurement. Positive screens require
confirmatory sweat chloride testing.
diagnosis_term:
preferred_term: disease screening
term:
id: MAXO:0000124
label: disease screening
notes: Enables early diagnosis and treatment, improving outcomes. False
negatives can occur with meconium ileus.
evidence:
- reference: PMID:28576637
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "In screen positive babies, the diagnosis of CF must be confirmed by a
sweat test demonstrating a sweat chloride concentration above 60mmol/L."
explanation: Supports newborn screening as an entry point that requires
confirmatory sweat chloride testing.
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Most cases of CF are identified through newborn screening (NBS). There
are also infants with positive NBS but inconclusive diagnostic testing; a small
proportion of these infants may go on to develop CF."
explanation: Clinical review confirms newborn screening as primary route to
CF diagnosis and notes inconclusive cases.
- name: Nasal Potential Difference
description: >-
Measurement of transepithelial voltage across nasal mucosa before and after
perfusion with chloride-free solution and isoproterenol. Abnormal pattern
(hyperpolarized baseline, absent chloride-free response) supports CFTR
dysfunction. Used as ancillary diagnostic test in borderline cases.
diagnosis_term:
preferred_term: transepithelial nasal potential difference measurement
term:
id: MAXO:0020006
label: Transepithelial nasal potential difference measurement
notes: Available only at specialized centers. Technically demanding.
evidence:
- reference: PMID:28576637
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "These patients should be referred to expert centers where bioassays of
CFTR function like nasal potential difference measurement or intestinal current
measurement can be done."
explanation: Supports nasal potential difference as a specialized test for
diagnostically inconclusive cases.
- reference: PMID:35163362
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Ex vivo and in vivo assays similarly evaluate current (intestinal current
measurement) and membrane potential differences (nasal potential difference),
on tissues from individual patients."
explanation: Confirms NPD as a recognized CFTR functional assay used in
diagnostic evaluation.
- name: Intestinal Current Measurement
description: >-
Ex vivo measurement of CFTR-mediated chloride transport in rectal biopsy tissue.
Provides direct assessment of CFTR function. Used in research settings and for
diagnosis in cases with inconclusive sweat chloride.
diagnosis_term:
preferred_term: rectal biopsy-based intestinal current measurement
term:
id: MAXO:0000398
label: biopsy of rectum
notes: Primarily available in European centers. Highly sensitive and specific.
evidence:
- reference: PMID:40943780
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Intestinal Current Measurement (ICM) is a novel diagnostic technique that
may document the abnormal function of the cystic fibrosis transmembrane conductance
regulator."
explanation: Directly supports ICM as a CFTR-function diagnostic technique.
- reference: PMID:40943780
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "The conducted study suggests that ICM may offer diagnostic value, especially
in cases where sweat test results are equivocal."
explanation: Supports using ICM as an adjunctive test when sweat chloride
results are borderline.
differential_diagnoses:
- name: Primary ciliary dyskinesia
disease_term:
preferred_term: primary ciliary dyskinesia
term:
id: MONDO:0016575
label: primary ciliary dyskinesia
description: >-
Primary ciliary dyskinesia can closely resemble cystic fibrosis with chronic
sinopulmonary symptoms driven by impaired mucociliary clearance.
distinguishing_features:
- CF is caused by CFTR dysfunction, whereas primary ciliary dyskinesia is caused by structural/functional ciliary defects.
- PCD is generally less prevalent than CF and requires a different specialist diagnostic work-up and management strategy.
evidence:
- reference: PMID:36828173
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Cystic fibrosis (CF) and Primary ciliary dyskinesia (PCD) are both rare
chronic diseases, inherited disorders associated with multiple complications,
namely respiratory complications, due to impaired mucociliary clearance that
affect severely patients' lives."
explanation: Supports major clinical overlap in respiratory presentations that
necessitates differential diagnosis.
- name: Asthma
disease_term:
preferred_term: asthma
term:
id: MONDO:0004979
label: asthma
description: >-
Asthma may overlap with CF pulmonary symptoms, especially wheeze and dyspnea,
and can complicate interpretation of obstructive respiratory findings.
distinguishing_features:
- CF diagnosis requires evidence of CFTR dysfunction (e.g., sweat chloride and/or genotype), while isolated asthma does not.
- CF-asthma overlap remains debated, so objective CFTR-focused testing is needed when symptoms overlap.
evidence:
- reference: PMID:33560464
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Respiratory symptoms for both CF and asthma include cough, wheezing, and
dyspnea."
explanation: Confirms direct symptom overlap between CF and asthma, supporting
asthma as an important differential diagnosis.
- name: Non-cystic fibrosis bronchiectasis
disease_term:
preferred_term: non-cystic fibrosis bronchiectasis
term:
id: MONDO:0004822
label: bronchiectasis
description: >-
Non-CF bronchiectasis can phenocopy CF-related chronic productive cough and
recurrent respiratory exacerbations but arises from heterogeneous non-CF
etiologies.
distinguishing_features:
- Etiologic evaluation in non-CF bronchiectasis emphasizes alternative causes (e.g., prior infection, immunodeficiency, autoimmune disease, PCD) rather than CFTR-confirmed disease.
- Non-CF bronchiectasis prevalence increases strongly with age, whereas CF is usually identified earlier in life through newborn screening or pediatric symptoms.
evidence:
- reference: PMID:40293759
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Non-cystic fibrosis (CF) bronchiectasis is a chronic lung condition caused
by permanent bronchial dilatation and inflammation and is characterized by daily
cough, sputum, and recurrent exacerbations."
explanation: Supports overlapping chronic respiratory presentation with CF and
the need to differentiate CF from non-CF bronchiectatic disease.
- name: CFTR-related metabolic syndrome (CRMS/CFSPID)
disease_term:
preferred_term: CFTR-related metabolic syndrome
term:
id: MONDO:0100627
label: CFTR-related metabolic syndrome
description: >-
CRMS/CFSPID is a diagnostic boundary condition identified after positive newborn
screening when available testing does not yet establish definitive cystic
fibrosis.
distinguishing_features:
- Patients with CRMS/CFSPID have inconclusive findings rather than definitive CF diagnosis at initial evaluation.
- Follow-up and additional functional testing are often required to determine whether patients evolve toward CF, CFTR-related disorder, or non-CF classification.
evidence:
- reference: PMID:40943780
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "The term 'cystic fibrosis transmembrane conductance regulator-related
metabolic syndrome/cystic fibrosis screen positive, inconclusive diagnosis
(CRMS/CFSPID)' refers to patients with positive screening tests but without
a final diagnosis of Cystic Fibrosis (CF)."
explanation: Directly supports CRMS/CFSPID as a key differential category when
CF diagnosis remains unresolved after positive screening.
environmental:
- name: Pseudomonas aeruginosa
description: >-
The most important pathogen in CF lung disease. Initial acquisition of
non-mucoid strains progresses to chronic infection with mucoid, alginate-producing
phenotypes that form antibiotic-resistant biofilms. Chronic Pseudomonas infection
is associated with accelerated decline in lung function and increased mortality.
Early eradication protocols aim to delay chronic colonization.
notes: Transition from non-mucoid to mucoid phenotype is a milestone event in
CF.
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Cystic fibrosis (CF) is an autosomal recessive disease characterized
by pancreatic insufficiency and chronic endobronchial airway infection."
explanation: Chronic endobronchial infection including Pseudomonas is a
defining characteristic of CF.
- name: Staphylococcus aureus
description: >-
Often the first pathogen to colonize CF airways in infancy. Both
methicillin-sensitive (MSSA) and methicillin-resistant (MRSA) strains are
common. MRSA infection is associated with worse lung function outcomes.
notes: Most common respiratory pathogen in young CF children.
evidence:
- reference: PMID:33526571
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Clinical characteristics include progressive obstructive lung disease,
sinusitis, exocrine pancreatic insufficiency leading to malabsorption and malnutrition,
liver and pancreatic dysfunction, and male infertility."
explanation: Progressive obstructive lung disease is driven by chronic
bacterial infections including S. aureus.
- name: Burkholderia cepacia complex
description: >-
Highly virulent group of gram-negative bacteria associated with rapid and
sometimes fatal decline in lung function (cepacia syndrome). Patient-to-patient
transmission necessitates strict infection control measures. B. cenocepacia
(genomovar III) is the most virulent species and is a relative contraindication
to lung transplantation at many centers.
notes: Infection control and patient segregation are critical.
evidence:
- reference: PMID:33526571
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Clinical characteristics include progressive obstructive lung disease,
sinusitis, exocrine pancreatic insufficiency leading to malabsorption and malnutrition,
liver and pancreatic dysfunction, and male infertility."
explanation: Progressive lung disease can be accelerated by virulent
pathogens like Burkholderia.
- name: Non-tuberculous Mycobacteria
description: >-
Mycobacterium abscessus complex and Mycobacterium avium complex are increasingly
recognized in CF. M. abscessus is particularly concerning due to treatment
resistance, potential for progressive lung disease, and may complicate lung
transplant candidacy.
notes: Screening sputum cultures recommended annually.
evidence:
- reference: PMID:33526571
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Clinical characteristics include progressive obstructive lung disease,
sinusitis, exocrine pancreatic insufficiency leading to malabsorption and malnutrition,
liver and pancreatic dysfunction, and male infertility."
explanation: Progressive obstructive lung disease involves various pathogens
including non-tuberculous mycobacteria.
- name: Aspergillus fumigatus
description: >-
Fungal colonization of CF airways that can trigger allergic bronchopulmonary
aspergillosis (ABPA), an IgE-mediated hypersensitivity response causing
worsening airflow obstruction and central bronchiectasis.
notes: ABPA requires treatment with systemic corticosteroids and antifungal
agents.
evidence:
- reference: PMID:33526571
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Clinical characteristics include progressive obstructive lung disease,
sinusitis, exocrine pancreatic insufficiency leading to malabsorption and malnutrition,
liver and pancreatic dysfunction, and male infertility."
explanation: Progressive obstructive lung disease includes complications
from fungal colonization.
- name: Tobacco Smoke Exposure
description: >-
Both active and passive tobacco smoke exposure accelerates lung function
decline in CF patients. Environmental tobacco smoke is a significant modifiable
risk factor, especially in children.
notes: Strict avoidance counseling is part of standard CF care.
evidence:
- reference: PMID:33526571
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Although CF is a life-shortening disease, survival has continued to
improve to a median age of 46.2 years due to earlier diagnosis through routine
newborn screening, promulgation of evidence-based guidelines to optimize nutritional
and pulmonary health, and the development of CF-specific interdisciplinary care
centers."
explanation: Evidence-based guidelines include avoidance of environmental
risk factors like tobacco smoke.
- name: Air Pollution
description: >-
Ambient air pollution (particulate matter, ozone, nitrogen dioxide) is
associated with increased pulmonary exacerbation rates and accelerated lung
function decline in CF.
notes: Epidemiologic association; exposure minimization recommended.
evidence:
- reference: PMID:33526571
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Although CF is a life-shortening disease, survival has continued to
improve to a median age of 46.2 years due to earlier diagnosis through routine
newborn screening, promulgation of evidence-based guidelines to optimize nutritional
and pulmonary health, and the development of CF-specific interdisciplinary care
centers."
explanation: Optimization of pulmonary health includes minimizing
environmental exposures.
treatments:
- name: Elexacaftor-Tezacaftor-Ivacaftor (Trikafta/Kaftrio)
description: >-
Triple combination CFTR modulator therapy containing two correctors
(elexacaftor, tezacaftor) that improve F508del-CFTR folding and trafficking
to the cell surface, plus a potentiator (ivacaftor) that increases channel
open probability. Approved for patients aged 2+ years with at least one
F508del allele, covering approximately 90% of CF patients. Produces dramatic
improvements in lung function, nutritional status, and quality of life.
evidence:
- reference: PMID:31697873
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Elexacaftor-tezacaftor-ivacaftor, relative to placebo, resulted in a
percentage of predicted FEV1 that was 13.8 points higher at 4 weeks and 14.3
points higher through 24 weeks, a rate of pulmonary exacerbations that was 63%
lower"
explanation: Phase 3 RCT demonstrates significant improvement in lung
function and 63% reduction in pulmonary exacerbations with Trikafta.
- reference: PMID:31697873
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "a respiratory domain score on the Cystic Fibrosis Questionnaire-Revised...that
was 20.2 points higher, and a sweat chloride concentration that was 41.8 mmol
per liter lower"
explanation: Trikafta also improves quality of life scores and reduces sweat
chloride, a biomarker of CFTR function.
treatment_term:
preferred_term: pharmacotherapy
term:
id: MAXO:0000058
label: pharmacotherapy
therapeutic_agent:
- preferred_term: elexacaftor
term:
id: NCIT:C169935
label: Elexacaftor
- preferred_term: tezacaftor
term:
id: NCIT:C152581
label: Tezacaftor
- preferred_term: ivacaftor
term:
id: CHEBI:66901
label: ivacaftor
- name: Ivacaftor (Kalydeco)
description: >-
CFTR potentiator that increases the channel open probability of CFTR protein
at the cell surface. First approved CFTR modulator, initially for G551D
mutation and subsequently expanded to other gating mutations. As monotherapy,
effective only for mutations where CFTR reaches the cell surface
(Class III, IV, V mutations).
evidence:
- reference: PMID:22047557
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "The change from baseline through week 24 in the percent of predicted
FEV(1) was greater by 10.6 percentage points in the ivacaftor group than in
the placebo group (P<0.001)."
explanation: Landmark Phase 3 trial demonstrating sustained lung function
improvement with ivacaftor in G551D patients.
treatment_term:
preferred_term: pharmacotherapy
term:
id: MAXO:0000058
label: pharmacotherapy
therapeutic_agent:
- preferred_term: ivacaftor
term:
id: CHEBI:66901
label: ivacaftor
- name: Airway Clearance Therapy
description: >-
Chest physiotherapy techniques to mobilize and clear airway secretions.
Includes manual chest percussion and postural drainage, oscillating positive
expiratory pressure devices (e.g., Flutter, Acapella), high-frequency chest
wall oscillation vests, autogenic drainage, and regular exercise. Performed
at least twice daily.
evidence:
- reference: PMID:33526571
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Although CF is a life-shortening disease, survival has continued to
improve to a median age of 46.2 years due to earlier diagnosis through routine
newborn screening, promulgation of evidence-based guidelines to optimize nutritional
and pulmonary health, and the development of CF-specific interdisciplinary care
centers."
explanation: Evidence-based guidelines for pulmonary health include airway
clearance therapies.
treatment_term:
preferred_term: physical therapy
term:
id: MAXO:0000011
label: physical therapy
- name: Dornase Alfa (Pulmozyme)
description: >-
Inhaled recombinant human DNase that cleaves extracellular DNA released from
necrotic neutrophils in CF sputum, reducing mucus viscosity and improving
airway clearance. Recommended for daily use in most CF patients.
evidence:
- reference: PMID:8874241
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Dornase alfa improved the mean percent change in FEV1 from baseline
by 9.4% compared with 2.1% for placebo (p < 0.001)."
explanation: Randomized controlled trial demonstrates significant
improvement in lung function with dornase alfa.
treatment_term:
preferred_term: pharmacotherapy
term:
id: MAXO:0000058
label: pharmacotherapy
therapeutic_agent:
- preferred_term: dornase alfa
term:
id: NCIT:C81664
label: Dornase Alfa
- name: Hypertonic Saline (7%)
description: >-
Inhaled nebulized hypertonic saline that osmotically draws water onto the
airway surface, rehydrating the periciliary layer and improving mucociliary
clearance. Used as adjunctive therapy to improve mucus mobilization.
evidence:
- reference: PMID:33526571
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Although CF is a life-shortening disease, survival has continued to
improve to a median age of 46.2 years due to earlier diagnosis through routine
newborn screening, promulgation of evidence-based guidelines to optimize nutritional
and pulmonary health, and the development of CF-specific interdisciplinary care
centers."
explanation: Evidence-based therapies for pulmonary health include mucolytic
agents like hypertonic saline.
treatment_term:
preferred_term: pharmacotherapy
term:
id: MAXO:0000058
label: pharmacotherapy
- name: Inhaled Antibiotics
description: >-
Chronic suppressive inhaled antibiotic therapy for patients with chronic
Pseudomonas aeruginosa infection. Inhaled tobramycin (alternating months)
and inhaled aztreonam lysine are most commonly used. Reduces bacterial
density, decreases pulmonary exacerbations, and preserves lung function.
evidence:
- reference: PMID:33526571
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Although CF is a life-shortening disease, survival has continued to
improve to a median age of 46.2 years due to earlier diagnosis through routine
newborn screening, promulgation of evidence-based guidelines to optimize nutritional
and pulmonary health, and the development of CF-specific interdisciplinary care
centers."
explanation: Improved survival reflects evidence-based treatments including
inhaled antibiotics for chronic infection.
treatment_term:
preferred_term: pharmacotherapy
term:
id: MAXO:0000058
label: pharmacotherapy
- name: Systemic Antibiotics
description: >-
Oral and intravenous antibiotics for acute pulmonary exacerbations and
chronic suppressive therapy. Azithromycin is used chronically for its
anti-inflammatory and anti-Pseudomonal properties. IV antibiotic courses
(typically 14-21 days) target specific pathogens identified on sputum culture.
evidence:
- reference: PMID:33526571
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Although CF is a life-shortening disease, survival has continued to
improve to a median age of 46.2 years due to earlier diagnosis through routine
newborn screening, promulgation of evidence-based guidelines to optimize nutritional
and pulmonary health, and the development of CF-specific interdisciplinary care
centers."
explanation: Evidence-based care includes systemic antibiotics for treating
pulmonary exacerbations.
treatment_term:
preferred_term: pharmacotherapy
term:
id: MAXO:0000058
label: pharmacotherapy
- name: Pancreatic Enzyme Replacement Therapy (PERT)
description: >-
Oral pancreatic enzyme supplements (lipase, protease, amylase) taken with
all meals and snacks to replace deficient endogenous enzymes. Dosing is
individualized based on fat intake and symptoms. Essential for maintaining
adequate nutrition in pancreatic-insufficient patients.
evidence:
- reference: PMID:33526571
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Although CF is a life-shortening disease, survival has continued to
improve to a median age of 46.2 years due to earlier diagnosis through routine
newborn screening, promulgation of evidence-based guidelines to optimize nutritional
and pulmonary health, and the development of CF-specific interdisciplinary care
centers."
explanation: Optimization of nutritional health includes pancreatic enzyme
replacement therapy.
treatment_term:
preferred_term: pharmacotherapy
term:
id: MAXO:0000058
label: pharmacotherapy
- name: Nutritional Support
description: >-
High-calorie, high-fat diet with fat-soluble vitamin supplementation (A, D, E,
K)
and sodium chloride supplementation. CF patients have increased caloric
requirements (120-150% of normal) due to malabsorption, chronic infection,
and increased work of breathing. Enteral tube feeding may be needed for
patients unable to maintain adequate weight.
evidence:
- reference: PMID:33526571
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Although CF is a life-shortening disease, survival has continued to
improve to a median age of 46.2 years due to earlier diagnosis through routine
newborn screening, promulgation of evidence-based guidelines to optimize nutritional
and pulmonary health, and the development of CF-specific interdisciplinary care
centers."
explanation: Evidence-based guidelines emphasize optimization of nutritional
health for CF patients.
treatment_term:
preferred_term: dietary intervention
term:
id: MAXO:0000088
label: dietary intervention
- name: Insulin Therapy for CFRD
description: >-
Insulin is the recommended treatment for CF-related diabetes. Oral
hypoglycemic agents are generally not recommended as primary therapy
due to the predominantly insulin-deficient pathophysiology. Insulin
improves nutritional status and lung function in addition to
glycemic control.
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Other complications include sinusitis, diabetes mellitus, bowel obstruction,
hepatobiliary disease, hyponatremic dehydration, and infertility."
explanation: CF-related diabetes is an established complication requiring
insulin therapy.
treatment_term:
preferred_term: pharmacotherapy
term:
id: MAXO:0000058
label: pharmacotherapy
- name: Ursodeoxycholic Acid
description: >-
Hydrophilic bile acid used to improve bile flow and potentially slow
progression of CF liver disease. Commonly prescribed for patients with
elevated liver enzymes or evidence of focal biliary cirrhosis, though
evidence for long-term clinical benefit is limited.
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Other complications include sinusitis, diabetes mellitus, bowel obstruction,
hepatobiliary disease, hyponatremic dehydration, and infertility."
explanation: Hepatobiliary disease in CF is treated with agents like
ursodeoxycholic acid.
treatment_term:
preferred_term: pharmacotherapy
term:
id: MAXO:0000058
label: pharmacotherapy
- name: Lung Transplantation
description: >-
Bilateral lung transplantation is offered for end-stage CF lung disease
when predicted survival without transplant is limited (typically FEV1 <30%
predicted with rapid decline). Five-year survival after transplant is
approximately 50-60%. CF lung disease does not recur in the transplanted lungs,
but immunosuppression-related complications and chronic rejection (bronchiolitis
obliterans syndrome) limit long-term outcomes.
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "This latter feature results in progressive bronchiectasis and ultimately
respiratory failure, which is the leading cause of death in patients with CF."
explanation: Respiratory failure as the leading cause of death necessitates
lung transplantation for end-stage disease.
treatment_term:
preferred_term: organ transplantation
term:
id: MAXO:0010039
label: organ transplantation
- name: Genetic Counseling
description: >-
Counseling for patients and families regarding autosomal recessive
inheritance, carrier testing for at-risk relatives, prenatal diagnosis
options, and reproductive planning. Carrier frequency is approximately
1 in 25 in European-descent populations.
treatment_term:
preferred_term: genetic counseling
term:
id: MAXO:0000079
label: genetic counseling
clinical_trials:
- name: NCT03525444
phase: PHASE_III
status: COMPLETED
description: >-
Phase 3, randomized, double-blind, placebo-controlled trial evaluating
elexacaftor-tezacaftor-ivacaftor in patients aged 12+ with cystic fibrosis
heterozygous for F508del and a minimal-function CFTR mutation. This landmark
trial led to FDA approval of Trikafta.
target_phenotypes:
- preferred_term: Bronchiectasis
term:
id: HP:0002110
label: Bronchiectasis
- preferred_term: Recurrent respiratory infections
term:
id: HP:0002205
label: Recurrent respiratory infections
evidence:
- reference: PMID:31697873
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Elexacaftor-tezacaftor-ivacaftor was efficacious in patients with cystic
fibrosis with Phe508del-minimal function genotypes, in whom previous CFTR modulator
regimens were ineffective."
explanation: This Phase 3 trial established efficacy of Trikafta for CF
patients with one F508del allele plus a minimal-function mutation.
has_subtypes:
# CFTR mutation class subtypes
- name: Class I - No Protein Production
classification: mutation_class
description: >-
Nonsense mutations, frameshift mutations, and canonical splice site mutations
that result in premature termination codons and no functional CFTR protein
production due to mRNA degradation via nonsense-mediated decay. Examples include
G542X, W1282X, R553X, and 621+1G>T. Class I mutations cause severe disease
with pancreatic insufficiency.
children:
- G542X
- W1282X
- R553X
evidence:
- reference: PMID:27053340
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "An effective, although not yet entirely corrective, treatment is available
for patients with class III mutations, and a treatment with modest effectiveness
is available for patients who are homozygous for Phe508del, albeit at a very
high cost."
explanation: Review discusses CFTR mutation classes and their therapeutic
implications, establishing the classification system.
- name: Class II - Processing/Trafficking Defect
classification: mutation_class
description: >-
Mutations causing CFTR protein misfolding, endoplasmic reticulum retention, and
proteasomal degradation. The most important example is F508del, present in nearly
90% of CF patients. Misfolded protein is recognized by ER quality control and
targeted for ubiquitin-proteasome degradation, resulting in minimal CFTR at the
cell surface. Corrector drugs (lumacaftor, tezacaftor, elexacaftor) partially
rescue F508del trafficking.
children:
- F508del
- N1303K
- I507del
evidence:
- reference: PMID:31697873
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "nearly 90% of patients have at least one copy of the Phe508del CFTR
mutation"
explanation: Confirms the high prevalence of the prototypical Class II
mutation F508del.
- name: Class III - Gating Defect
classification: mutation_class
description: >-
CFTR protein reaches the cell surface normally but channel gating is severely
impaired, resulting in very low open probability. The prototypical example is
G551D. Potentiator drugs (ivacaftor) increase channel open probability and
produce dramatic clinical benefit.
children:
- G551D
- S549N
- G1244E
evidence:
- reference: PMID:22047557
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "The change from baseline through week 24 in the percent of predicted
FEV(1) was greater by 10.6 percentage points in the ivacaftor group than in
the placebo group (P<0.001)."
explanation: Ivacaftor trial in G551D patients demonstrates therapeutic
targeting of gating mutations.
- name: Class IV - Conductance Defect
classification: mutation_class
description: >-
CFTR reaches the cell surface and channel opens, but chloride conductance
through the channel pore is reduced. Typically associated with milder phenotype
and pancreatic sufficiency. Examples include R117H, R334W, and R347P.
children:
- R117H
- R334W
- R347P
evidence:
- reference: PMID:27053340
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "An effective, although not yet entirely corrective, treatment is available
for patients with class III mutations, and a treatment with modest effectiveness
is available for patients who are homozygous for Phe508del, albeit at a very
high cost."
explanation: Review describes mutation class-specific treatments, including
Class IV conductance defects.
- name: Class V - Reduced Quantity
classification: mutation_class
description: >-
Mutations that reduce the amount of normal CFTR protein produced, such as
alternative splice site mutations that produce some normal transcript alongside
aberrant transcript. Typically associated with milder phenotype and pancreatic
sufficiency. Examples include 3849+10kbC>T and A455E.
children:
- 3849+10kbC>T
- A455E
evidence:
- reference: PMID:27053340
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "An effective, although not yet entirely corrective, treatment is available
for patients with class III mutations, and a treatment with modest effectiveness
is available for patients who are homozygous for Phe508del, albeit at a very
high cost."
explanation: Review discusses the classification system and mutation
classes.
- name: Class VI - Decreased Stability
classification: mutation_class
description: >-
CFTR protein reaches the cell surface and functions but has accelerated
turnover and reduced plasma membrane stability. Rescued F508del protein
(after corrector therapy) exhibits this additional defect, necessitating
combination therapy with correctors and potentiators.
evidence:
- reference: PMID:37699417
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "With the 2019 breakthrough in the development of highly effective modulator
therapy providing unprecedented clinical benefits for over 90% of patients with
cystic fibrosis who are genetically eligible for treatment, this rare disease
has become a front runner of transformative molecular therapy."
explanation: Review discusses CFTR modulator therapy addressing multiple
defects including decreased stability.
# Clinical phenotype subtypes
- name: Classic Cystic Fibrosis
classification: clinical_phenotype
description: >-
Severe disease phenotype with two severe CFTR mutations, pancreatic insufficiency,
progressive bronchiectasis, elevated sweat chloride (>=60 mmol/L), and male
infertility due to CBAVD. Represents the majority of CF patients.
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Cystic fibrosis (CF) is an autosomal recessive disease characterized
by pancreatic insufficiency and chronic endobronchial airway infection."
explanation: Clinical review describes the classic CF phenotype of
pancreatic insufficiency and chronic airway infection.
- name: Atypical (Non-Classic) Cystic Fibrosis
classification: clinical_phenotype
description: >-
Milder disease phenotype, often with at least one CFTR mutation conferring
residual function (Class IV, V). May present with pancreatic sufficiency,
milder lung disease, borderline or normal sweat chloride, and later age of
diagnosis. Some patients are not diagnosed until adulthood.
evidence:
- reference: PMID:33178516
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Cystic fibrosis (CF) is an autosomal recessive, multi-organ disorder
found predominantly among Caucasians."
explanation: Case report of atypical CF diagnosis at age 57, illustrating
the spectrum of disease severity and late diagnosis in non-classic
presentations.
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "There are also infants with positive NBS but inconclusive diagnostic
testing; a small proportion of these infants may go on to develop CF."
explanation: Some individuals with inconclusive diagnostic testing have
milder, atypical presentations that may evolve over time.
- name: CFTR-Related Metabolic Syndrome (CRMS) / CF Screen Positive Inconclusive
Diagnosis (CFSPID)
classification: clinical_phenotype
description: >-
Designation for infants identified by newborn screening who do not meet
diagnostic criteria for CF but have some evidence of CFTR dysfunction.
Defined as either intermediate sweat chloride (30-59 mmol/L) with fewer than
two CF-causing CFTR mutations, or normal sweat chloride (<30 mmol/L) with
two CFTR mutations of which at least one has unclear clinical significance.
A small proportion may evolve to a CF diagnosis over time. Requires longitudinal
monitoring.
evidence:
- reference: PMID:30986316
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "There are also infants with positive NBS but inconclusive diagnostic
testing; a small proportion of these infants may go on to develop CF."
explanation: Clinical review describes the scenario of inconclusive CF
diagnosis after positive newborn screening.
- reference: PMID:28129811
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Cystic fibrosis (CF), caused by mutations in the CF transmembrane conductance
regulator (CFTR) gene, continues to present diagnostic challenges."
explanation: CF Foundation guidelines address diagnostic challenges
including CRMS/CFSPID designation.
# CFTR-related disorders
- name: Congenital Bilateral Absence of the Vas Deferens (CBAVD)
classification: CFTR_related_disorder
description: >-
Isolated congenital bilateral absence of the vas deferens causing obstructive
azoospermia and male infertility, without other features of classic CF. Found
in approximately 1-2% of infertile males. Most affected men carry at least
one CFTR mutation, often including the 5T poly-T variant or R117H. Sweat
chloride is typically normal or borderline. Lung and pancreatic function
are preserved.
- name: CFTR-Related Pancreatitis
classification: CFTR_related_disorder
description: >-
Recurrent acute or chronic pancreatitis in individuals carrying one or two
CFTR mutations with residual function, without meeting diagnostic criteria
for CF. CFTR dysfunction impairs bicarbonate secretion in pancreatic ducts,
predisposing to ductal obstruction and pancreatitis. Sweat chloride is
typically normal or borderline.
- name: CFTR-Related Disseminated Bronchiectasis
classification: CFTR_related_disorder
description: >-
Diffuse bronchiectasis in individuals carrying CFTR mutations who do not
meet diagnostic criteria for CF. Sweat chloride may be normal or borderline.
Represents the milder end of the CFTR dysfunction spectrum affecting
the airways.
notes: >-
Cystic fibrosis care has been transformed by CFTR modulator therapy, particularly
elexacaftor-tezacaftor-ivacaftor (Trikafta), which provides substantial clinical
benefit for approximately 90% of CF patients. Median survival has increased from
early childhood death to beyond 40 years, with further improvements expected.
Multidisciplinary care at specialized CF centers remains essential, encompassing
pulmonary, nutritional, endocrine, hepatic, and psychosocial aspects. The CF
Foundation accredits specialized care centers and maintains registries that drive
quality improvement. Remaining therapeutic challenges include patients with
nonsense mutations (Class I) not responsive to current modulators, established
lung damage in older patients, and long-term effects of CFTR modulator therapy.
Gene therapy and mRNA-based approaches are under active investigation for patients
with mutations not amenable to small molecule modulation.
disease_term:
preferred_term: cystic fibrosis
term:
id: MONDO:0009061
label: cystic fibrosis
classifications:
harrisons_chapter:
- classification_value: respiratory system disorder
- classification_value: hereditary disease
experimental_models:
- name: Patient-derived airway organoid theratyping model
description: >-
Patient-derived nasal epithelial stem cells expanded from nasal brushings
and differentiated into airway organoids for personalized CFTR modulator
response testing.
experimental_model_type: ORGANOID
namo_type: namo:Organoid
organism:
preferred_term: human
term:
id: NCBITaxon:9606
label: Homo sapiens
tissue_term:
preferred_term: respiratory airway
term:
id: UBERON:0001005
label: respiratory airway
conditions:
- cystic fibrosis
- CFTR modulator theratyping
cell_source: Patient-derived nasal epithelial stem cells obtained by nasal brushing
culture_system: 3D airway organoids linked to differentiated air-liquid interface cultures
publication: PMID:34413153
modeled_mechanisms:
- target: CFTR Dysfunction
description: Measures genotype-specific epithelial CFTR dysfunction and rescue by modulators in patient-derived airway tissue.
findings:
- statement: Patient-derived airway organoids enable genotype-specific CFTR modulator response testing, including rare genotypes
evidence:
- reference: PMID:34413153
supports: SUPPORT
evidence_source: IN_VITRO
snippet: "We exploited an innovative cellular approach allowing highly efficient in vitro expansion of airway epithelial stem cells (AESCs) through conditional reprogramming from nasal brushing of CF patients."
explanation: Supports use of patient-derived airway organoids for CFTR theratyping in a genotype-specific epithelial system.
- reference: PMID:35922154
supports: SUPPORT
evidence_source: IN_VITRO
snippet: "we therefore describe an alternative method of culturing nasal-brushing-derived airway organoids, which are created from an equally differentiated airway epithelial monolayer of a 2D air-liquid interface culture"
explanation: Supports reproducible CFTR functional readouts from nasal-brushing-derived airway organoid cultures.
evidence:
- reference: PMID:34413153
supports: SUPPORT
evidence_source: IN_VITRO
snippet: "We exploited an innovative cellular approach allowing highly efficient in vitro expansion of airway epithelial stem cells (AESCs) through conditional reprogramming from nasal brushing of CF patients."
explanation: Supports this as a disease-relevant patient-derived organoid model system for CF.
- name: CF airway-on-chip microphysiological model
description: >-
Human microfluidic airway chip lined by primary CF bronchial epithelial
cells and pulmonary microvascular endothelial cells, recapitulating mucus,
inflammation, and infection phenotypes under air-liquid interface culture.
experimental_model_type: ORGAN_ON_CHIP
namo_type: namo:OrganOnChip
organism:
preferred_term: human
term:
id: NCBITaxon:9606
label: Homo sapiens
tissue_term:
preferred_term: bronchial epithelium
term:
id: UBERON:0002031
label: epithelium of bronchus
cell_types:
- preferred_term: Bronchial epithelial cell
term:
id: CL:0002328
label: bronchial epithelial cell
conditions:
- cystic fibrosis
- healthy control
- Pseudomonas aeruginosa infection modeling
cell_source: Primary human CF bronchial epithelial cells with pulmonary microvascular endothelial coculture
culture_system: Microfluidic organ-on-chip with air-liquid interface airway compartment
publication: PMID:34799298
modeled_mechanisms:
- target: Airway Surface Liquid Depletion
description: Recapitulates dehydrated mucus-layer phenotypes downstream of epithelial ion-transport failure.
- target: Impaired Mucociliary Clearance
description: Captures ciliary and mucus-transport abnormalities in differentiated CF airway epithelium.
- target: Chronic Bacterial Infection
description: Provides a controllable airway context for infection and bacterial overgrowth phenotypes in CF epithelium.
findings:
- statement: CF airway chips recapitulate mucus accumulation, ciliary abnormalities, inflammatory signaling, and bacterial overgrowth
evidence:
- reference: PMID:34799298
supports: SUPPORT
evidence_source: IN_VITRO
snippet: "The CF Airway Chip faithfully recapitulated many features of the human CF airways, including enhanced mucus accumulation, increased cilia density, and a higher ciliary beating frequency compared to chips lined by healthy bronchial epithelial cells."
explanation: Establishes the chip as a physiologically relevant CF airway model.
evidence:
- reference: PMID:34799298
supports: SUPPORT
evidence_source: IN_VITRO
snippet: "The CF Airway Chip faithfully recapitulated many features of the human CF airways, including enhanced mucus accumulation, increased cilia density, and a higher ciliary beating frequency compared to chips lined by healthy bronchial epithelial cells."
explanation: Supports inclusion of this organ-on-chip system as a CF-relevant experimental model.
- name: NuLi/CuFi airway epithelial cell-line model
description: >-
Immortalized human airway epithelial cell lines representing normal and CF
genotypes, differentiated at air-liquid interface to study ion transport
and innate immune phenotypes.
experimental_model_type: CELL_LINE
namo_type: namo:CellLineModel
organism:
preferred_term: human
term:
id: NCBITaxon:9606
label: Homo sapiens
tissue_term:
preferred_term: respiratory airway
term:
id: UBERON:0001005
label: respiratory airway
cell_types:
- preferred_term: Bronchial epithelial cell
term:
id: CL:0002328
label: bronchial epithelial cell
conditions:
- cystic fibrosis
- healthy control
cell_source: Immortalized human airway epithelial cell lines (NuLi-1, CuFi-1, CuFi-3, CuFi-4)
culture_system: Polarized differentiated air-liquid interface epithelial culture
publication: PMID:12676769
modeled_mechanisms:
- target: CFTR Dysfunction
description: Preserves genotype-specific CFTR-dependent ion-transport defects in a reusable airway epithelial system.
- target: ENaC Hyperactivity and Sodium Hyperabsorption
description: Supports mechanistic readouts of abnormal epithelial sodium transport downstream of CFTR loss.
findings:
- statement: NuLi and CuFi lines retain genotype-specific ion-transport and epithelial differentiation phenotypes in vitro
evidence:
- reference: PMID:12676769
supports: SUPPORT
evidence_source: IN_VITRO
snippet: "When grown at the air-liquid interface, the cell lines were capable of forming polarized differentiated epithelia that exhibited transepithelial resistance and maintained the ion channel physiology expected for the genotypes."
explanation: Confirms durable genotype-relevant airway epithelial physiology in a reusable CF cell-line model.
evidence:
- reference: PMID:12676769
supports: SUPPORT
evidence_source: IN_VITRO
snippet: "When grown at the air-liquid interface, the cell lines were capable of forming polarized differentiated epithelia that exhibited transepithelial resistance and maintained the ion channel physiology expected for the genotypes."
explanation: Supports inclusion of this cell-line system as a CF experimental model.
datasets:
- accession: geo:GSE150674
title: Transcriptional analysis of cystic fibrosis airways at single-cell resolution reveals altered epithelial cell states and composition
description: >-
Single-cell sequencing dataset of human airway epithelium from normal and
cystic fibrosis lungs, including donor airway samples used to define altered
epithelial cell-state composition in CF.
organism:
preferred_term: human
term:
id: NCBITaxon:9606
label: Homo sapiens
data_type: SINGLE_CELL_RNA_SEQ
sample_types:
- preferred_term: proximal airway epithelium
term:
id: UBERON:0001005
label: respiratory airway
tissue_term:
preferred_term: respiratory airway
term:
id: UBERON:0001005
label: respiratory airway
sample_count: 38
conditions:
- cystic fibrosis
- healthy control
publication: PMID:33958799
findings:
- statement: CF proximal airways show shifted epithelial-state composition with increased transitioning ciliated/secretory programs
evidence:
- reference: PMID:33958799
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Disease-dependent differences observed include an overabundance of epithelial cells transitioning to specialized ciliated and secretory cell subsets coupled with an unexpected decrease in cycling basal cells."
explanation: Single-cell airway profiling identifies disease-dependent epithelial state shifts in CF.
notes: Donor-cohort count from the linked Nat Med study (19 CF + 19 healthy proximal-airway donors); GEO may include additional technical records not counted as biological samples.
- accession: geo:GSE193782
title: ScRNA-seq Expression of APOC2 and IFI27 Identifies Four Alveolar Macrophage Superclusters in Cystic Fibrosis and Healthy BALF
description: >-
Single-cell RNA sequencing dataset of bronchoalveolar lavage cells from
healthy controls and uninflamed cystic fibrosis subjects used to define
alveolar macrophage superclusters and immune-cell heterogeneity.
organism:
preferred_term: human
term:
id: NCBITaxon:9606
label: Homo sapiens
data_type: SINGLE_CELL_RNA_SEQ
sample_types:
- preferred_term: lung (bronchoalveolar lavage cells)
term:
id: UBERON:0002048
label: lung
tissue_term:
preferred_term: lung
term:
id: UBERON:0002048
label: lung
sample_count: 7
conditions:
- cystic fibrosis
- healthy control
publication: PMID:35820705
findings:
- statement: BAL single-cell profiling identifies conserved alveolar macrophage superclusters across healthy and uninflamed CF subjects
evidence:
- reference: PMID:35820705
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "We performed single-cell RNA sequencing on 113,213 bronchoalveolar lavage cells from four healthy and three uninflamed cystic fibrosis subjects and identified two MARCKS+LGMN+IMs, FOLR2+SELENOP+ and SPP1+PLA2G7+ IMs, monocyte subtypes, DC1, DC2, migDCs, plasmacytoid DCs, lymphocytes, epithelial cells, and four AM superclusters (families) based on the gene expression of IFI27 and APOC2"
explanation: The study reports core BAL immune-cell architecture including four alveolar macrophage superclusters in CF-context samples.
notes: Provides CF-relevant BAL immune-cell state reference for airway inflammation mechanisms.
- accession: geo:GSE266789
title: "Early human fetal lung atlas reveals the temporal dynamics of epithelial cell plasticity [scRNAseq-hPSC]"
description: >-
Early human fetal lung single-cell atlas dataset profiling over 150,000
cells from gestational weeks 10-19, with trajectories of CFTR-expressing
progenitor populations and comparison to hPSC-derived fetal lung models.
organism:
preferred_term: human
term:
id: NCBITaxon:9606
label: Homo sapiens
data_type: SINGLE_CELL_RNA_SEQ
sample_types:
- preferred_term: fetal lung tissue
term:
id: UBERON:0002048
label: lung
tissue_term:
preferred_term: lung
term:
id: UBERON:0002048
label: lung
sample_count: 19
conditions:
- normal fetal development
publication: PMID:39003323
findings:
- statement: Fetal lung development includes CFTR-high progenitor trajectories that inform developmental context for CFTR biology
evidence:
- reference: PMID:39003323
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "We capture dynamic developmental trajectories from progenitor cells that express abundant levels of the cystic fibrosis conductance transmembrane regulator (CFTR)."
explanation: Establishes developmental CFTR-expressing progenitor trajectories relevant to CFTR biology.
notes: Developmental fetal-lung atlas with explicit CFTR-expressing progenitor characterization.
# CELLxGENE - CF and healthy control biopsy
- accession: "cellxgene:54004c5c-af08-4693-a606-73871b6ef989"
title: Cystic Fibrosis and healthy control biopsy
description: >-
Single-cell transcriptomic profiling of cystic fibrosis and healthy control
biopsies available on CZI CELLxGENE Discover. Provides disease-specific
cell state annotations for CF airway pathology.
organism:
preferred_term: human
term:
id: NCBITaxon:9606
label: Homo sapiens
data_type: SINGLE_CELL_RNA_SEQ
sample_types:
- preferred_term: airway biopsy
tissue_term:
preferred_term: lung
term:
id: UBERON:0002048
label: lung
conditions:
- cystic fibrosis
- healthy control
publication: DOI:10.1016/j.jcf.2025.01.016
notes: CZI CELLxGENE collection.
# --- Experimental / Organoid / Physiological Model Datasets (Issue #302) ---
- accession: doi:10.1111/liv.15963
title: Single-cell RNA sequencing of cystic fibrosis liver disease explants reveals endothelial complement activation
description: >-
Single-cell RNA sequencing of four CF liver disease explant livers identifying
differential endothelial characteristics including a distinct population of
liver sinusoidal endothelial cells upregulating complement cascade genes.
organism:
preferred_term: human
term:
id: NCBITaxon:9606
label: Homo sapiens
data_type: SINGLE_CELL_RNA_SEQ
sample_types:
- preferred_term: liver explant
term:
id: UBERON:0002107
label: liver
tissue_term:
preferred_term: liver
term:
id: UBERON:0002107
label: liver
sample_count: 4
conditions:
- cystic fibrosis liver disease
publication: PMID:38847551
findings:
- statement: CF liver explants contain a distinct population of sinusoidal endothelial cells with upregulated complement and coagulation genes
evidence:
- reference: PMID:38847551
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "we performed single-cell RNA sequencing (scRNA-seq) on four explant livers from CFLD patients to identify differential endothelial characteristics which could contribute to the disease"
explanation: First scRNA-seq characterization of endothelial involvement in CF liver disease.
notes: First comprehensive single-cell analysis of CF hepatic complications; supports endothelial involvement in CFLD.
- accession: doi:10.1183/13993003.00908-2021
title: Theratyping cystic fibrosis in ALI culture and organoid models from patient-derived nasal epithelial conditionally reprogrammed stem cells
description: >-
Patient-derived nasal epithelial stem cells expanded via conditional reprogramming
and used to generate 3D airway organoids and ALI cultures for personalized CFTR
modulator efficacy testing (theratyping).
organism:
preferred_term: human
term:
id: NCBITaxon:9606
label: Homo sapiens
data_type: MULTI_OMICS_PERTURBATION
sample_types:
- preferred_term: nasal epithelial organoid
term:
id: UBERON:0001005
label: respiratory airway
tissue_term:
preferred_term: nasal epithelium
term:
id: UBERON:0001005
label: respiratory airway
conditions:
- cystic fibrosis
publication: PMID:34413153
findings:
- statement: Conditionally reprogrammed nasal epithelial stem cells generate organoids suitable for personalized CFTR modulator testing
evidence:
- reference: PMID:34413153
supports: SUPPORT
evidence_source: IN_VITRO
snippet: "We exploited an innovative cellular approach allowing highly efficient in vitro expansion of airway epithelial stem cells (AESCs) through conditional reprogramming from nasal brushing of CF patients."
explanation: Demonstrates non-invasive patient-specific organoid model for personalized drug screening.
notes: Experimental model enabling theratyping for patients with rare CFTR genotypes not eligible for standard modulator therapy.
- accession: doi:10.26508/lsa.202101320
title: Measuring cystic fibrosis drug responses in organoids derived from 2D differentiated nasal epithelia
description: >-
Novel method for generating nasal-brushing-derived airway organoids from 2D
air-liquid interface cultures, enabling consistent detection of CFTR modulator
responses via forskolin-induced swelling assay.
organism:
preferred_term: human
term:
id: NCBITaxon:9606
label: Homo sapiens
data_type: MULTI_OMICS_PERTURBATION
sample_types:
- preferred_term: nasal epithelial organoid
term:
id: UBERON:0001005
label: respiratory airway
tissue_term:
preferred_term: nasal epithelium
term:
id: UBERON:0001005
label: respiratory airway
conditions:
- cystic fibrosis
publication: PMID:35922154
findings:
- statement: 2D-to-3D transition culture method enables consistent CFTR modulator response detection in nasal airway organoids
evidence:
- reference: PMID:35922154
supports: SUPPORT
evidence_source: IN_VITRO
snippet: "we therefore describe an alternative method of culturing nasal-brushing-derived airway organoids, which are created from an equally differentiated airway epithelial monolayer of a 2D air-liquid interface culture"
explanation: Combines advantages of ALI differentiation with 3D organoid FIS assay for improved scalability.
notes: Improved organoid culture protocol with neuregulin-1β and interleukin-1β for consistent CFTR functional readouts.
- accession: doi:10.26508/lsa.202201857
title: Validating organoid-derived human intestinal monolayers for personalized therapy in cystic fibrosis
description: >-
Validation of 2D human intestinal organoid monolayers as a preclinical drug
testing tool, demonstrating comparable CFTR functional responses across 2D HIO,
3D HIO, and HNE methods with good correlation to clinical outcome markers.
organism:
preferred_term: human
term:
id: NCBITaxon:9606
label: Homo sapiens
data_type: MULTI_OMICS_PERTURBATION
sample_types:
- preferred_term: intestinal organoid monolayer
term:
id: UBERON:0000160
label: intestine
tissue_term:
preferred_term: intestine
term:
id: UBERON:0000160
label: intestine
conditions:
- cystic fibrosis
publication: PMID:37024122
findings:
- statement: 2D intestinal organoid monolayers show comparable CFTR functional responses to 3D organoids and HNE cultures with good clinical correlation
evidence:
- reference: PMID:37024122
supports: SUPPORT
evidence_source: IN_VITRO
snippet: "This study is the first to report comparable CFTR functional responses to CFTR modulator treatment among patients with different classes of CFTR gene variants using the three methods of 2D HIO, 3D HIO, and HNE."
explanation: Expands utility of intestinal monolayers as scalable preclinical drug testing tool for CF.
notes: Demonstrates larger measurable CFTR functional range and apical membrane access advantages of 2D HIO over HNE and 3D HIO.
- accession: doi:10.1007/s00018-025-05627-7
title: Endometrium-derived organoids from cystic fibrosis patients and mice as new models to study disease-associated endometrial pathobiology
description: >-
Endometrial organoid models from CF patients and CF mice revealing molecular
and pathway differences in hormone responses, with single-cell RNA sequencing
of CF mouse uterus confirming similar molecular traits to human CF endometrium.
organism:
preferred_term: human
term:
id: NCBITaxon:9606
label: Homo sapiens
data_type: SINGLE_CELL_RNA_SEQ
sample_types:
- preferred_term: endometrial organoid
term:
id: UBERON:0001295
label: endometrium
tissue_term:
preferred_term: endometrium
term:
id: UBERON:0001295
label: endometrium
conditions:
- cystic fibrosis
- healthy control
publication: PMID:40074868
findings:
- statement: CF endometrial organoids recapitulate disease characteristics and reveal cycle-dependent molecular aberrations correctable by CFTR modulators
evidence:
- reference: PMID:40074868
supports: SUPPORT
evidence_source: IN_VITRO
snippet: "we developed organoid models from CF patient endometrium. The organoids recapitulated CF characteristics and revealed molecular and pathway differences in cycle-recapitulating hormone responses compared to healthy endometrial organoids."
explanation: Expands CF model systems beyond respiratory and GI to reproductive tissue pathobiology.
notes: Includes scRNA-seq of CF mouse uterus; relevant to CF fertility challenges and reproductive pathobiology.
- accession: doi:10.1016/j.jcf.2021.10.004
title: Modeling pulmonary cystic fibrosis in a human lung airway-on-a-chip
description: >-
Microfluidic organ-on-a-chip device lined by primary human CF bronchial
epithelial cells at air-liquid interface with pulmonary microvascular
endothelial cells, recapitulating CF airway pathophysiology including mucus
accumulation, inflammation, and Pseudomonas aeruginosa infection.
organism:
preferred_term: human
term:
id: NCBITaxon:9606
label: Homo sapiens
data_type: MULTI_OMICS_PERTURBATION
sample_types:
- preferred_term: bronchial epithelium on microfluidic chip
term:
id: UBERON:0002031
label: epithelium of bronchus
tissue_term:
preferred_term: bronchial epithelium
term:
id: UBERON:0002031
label: epithelium of bronchus
conditions:
- cystic fibrosis
- healthy control
publication: PMID:34799298
findings:
- statement: CF airway-on-a-chip recapitulates enhanced mucus accumulation, increased cilia density, higher IL-8 secretion, and enhanced Pseudomonas aeruginosa growth
evidence:
- reference: PMID:34799298
supports: SUPPORT
evidence_source: IN_VITRO
snippet: "The CF Airway Chip faithfully recapitulated many features of the human CF airways, including enhanced mucus accumulation, increased cilia density, and a higher ciliary beating frequency compared to chips lined by healthy bronchial epithelial cells."
explanation: Organ-on-chip platform enabling physiological CF modeling with infection and inflammation readouts.
notes: Organ-on-a-chip model from Wyss Institute; supports drug testing and personalized medicine applications.
- accession: doi:10.1152/ajplung.00355.2002
title: Development of cystic fibrosis and noncystic fibrosis airway cell lines (NuLi-1 and CuFi)
description: >-
Immortalized human airway epithelial cell lines derived from normal (NuLi-1)
and CF (CuFi-1, CuFi-3, CuFi-4) genotypes using hTERT and HPV-16 E6/E7,
capable of forming polarized differentiated epithelia at air-liquid interface.
organism:
preferred_term: human
term:
id: NCBITaxon:9606
label: Homo sapiens
data_type: MULTI_OMICS_PERTURBATION
sample_types:
- preferred_term: airway epithelial cell line
term:
id: UBERON:0001005
label: respiratory airway
tissue_term:
preferred_term: respiratory airway
term:
id: UBERON:0001005
label: respiratory airway
conditions:
- cystic fibrosis
- healthy control
publication: PMID:12676769
findings:
- statement: NuLi and CuFi cell lines maintain genotype-specific ion channel physiology and NF-kB innate immune responses at ALI
evidence:
- reference: PMID:12676769
supports: SUPPORT
evidence_source: IN_VITRO
snippet: "When grown at the air-liquid interface, the cell lines were capable of forming polarized differentiated epithelia that exhibited transepithelial resistance and maintained the ion channel physiology expected for the genotypes."
explanation: Immortalized CF cell lines supporting reproducible ion physiology and innate immunity studies.
notes: Immortalized CF cell line resource; CuFi lines are correctable by adenoviral CFTR vectors.