Cystic fibrosis (CF) is a genetic disorder inherited in an autosomal recessive manner that impairs the normal clearance of mucus from the lungs, which facilitates the colonization and infection of the lungs by bacteria, notably Pseudomonas aeruginosa and Staphylococcus aureus. CF is a rare genetic disorder that affects mostly the lungs, but also the pancreas, liver, kidneys, and intestine. The hallmark feature of CF is the accumulation of thick mucus in different organs. Long-term issues include difficulty breathing and coughing up mucus as a result of frequent lung infections. Other signs and symptoms may include sinus infections, poor growth, fatty stool, clubbing of the fingers and toes, and infertility in most males. Different people may have different degrees of symptoms. Cystic fibrosis is inherited in an autosomal recessive manner. It is caused by the presence of mutations in both copies (alleles) of the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR) protein. Those with a single working copy are carriers and otherwise mostly healthy. CFTR is involved in the production of sweat, digestive fluids, and mucus. When the CFTR is not functional, secretions that are usually thin instead become thick. The condition is diagnosed by a sweat test and genetic testing. The sweat test measures chloride concentration, as people with cystic fibrosis have abnormally salty sweat. Screening of infants at birth takes place in some areas of the world. There is no known cure for cystic fibrosis. CFTR modulators, oral medications that directly target defects in the CFTR protein, have substantially improved survival among people with eligible CFTR variants who have access to treatment. Lung infections are treated with antibiotics which may be given intravenously, inhaled, or by mouth. Sometimes, the antibiotic azithromycin is used long-term. Inhaled hypertonic saline and salbutamol may also be useful. Lung transplantation may be an option if lung function continues to worsen. Pancreatic enzyme replacement and fat-soluble vitamin supplementation are important, especially in the young. Airway clearance techniques such as chest physiotherapy may have some short-term benefit, but long-term effects are unclear. Recent improvements in treatment have contributed to a significant increase in estimated median survival to approximately 65 years in Canada, the US, and the UK. Lung problems account for approximately 30% of deaths among people with CF. CF is most common among people of Northern European ancestry, for whom it affects about 1 out of 3,000 newborns, and among which around 1 out of 25 people is a carrier. It is least common in Africa and Asia. It was first recognized as a specific disease by Dorothy Andersen in 1938, with descriptions that fit the condition occurring at least as far back as 1595. The name "cystic fibrosis" refers to the characteristic fibrosis and cysts that form within the pancreas.
Signs and symptoms
Cystic fibrosis typically manifests early in life. Newborns and infants with cystic fibrosis tend to have frequent, large, greasy stools (a result of malabsorption) and are underweight for their age. Of newborns, 15–20% have their small intestine blocked by meconium, often requiring surgery to correct. Newborns occasionally have neonatal jaundice due to blockage of the bile ducts. Children with cystic fibrosis lose excessive salt in their sweat, and parents notice salt crystallizing on the skin, or a salty taste when they kiss their child. The primary cause of morbidity and death in people with cystic fibrosis is progressive lung disease, which eventually leads to respiratory failure. This typically begins as a prolonged respiratory infection that continues until treated with antibiotics. Chronic infection of the respiratory tract is nearly universal in people with cystic fibrosis, with Pseudomonas aeruginosa, fungi, and mycobacteria all becoming increasingly common over time. Inflammation of the upper airway results in frequent runny nose and nasal obstruction. Nasal polyps are common, particularly in children and teenagers. As the disease progresses, people tend to have shortness of breath, and a chronic cough that produces sputum. Breathing problems make it increasingly challenging to exercise, and prolonged illness causes those affected to be underweight for their age. In late adolescence or adulthood, people begin to develop severe signs of lung disease: wheezing, digital clubbing, cyanosis, coughing up blood, pulmonary heart disease, and collapsed lung (atelectasis or pneumothorax). In rare cases, cystic fibrosis can manifest itself as a coagulation disorder. Vitamin K is normally absorbed from breast milk, formula, and later, solid foods. This absorption is impaired in some CF patients. Young children are especially sensitive to vitamin K malabsorptive disorders because only a very small amount of vitamin K crosses the placenta, leaving the child with very low reserves and limited ability to absorb vitamin K from dietary sources after birth. Because clotting factors II, VII, IX, and X are vitamin K–dependent, low levels of vitamin K can result in coagulation problems. Consequently, when a child presents with unexplained bruising, a coagulation evaluation may be warranted to determine whether an underlying disease is present.
Lungs and sinuses
Lung disease results from clogging of the airways due to mucus build-up, decreased mucociliary clearance, and resulting inflammation. In later stages, changes in the architecture of the lung, such as pathology in the major airways (bronchiectasis), further exacerbate difficulties in breathing. Other signs include high blood pressure in the lung (pulmonary hypertension), heart failure, difficulties getting enough oxygen to the body (hypoxia), and respiratory failure requiring support with breathing masks, such as bilevel positive airway pressure machines or ventilators. Staphylococcus aureus, Haemophilus influenzae, and Pseudomonas aeruginosa are the three most common organisms causing lung infections in CF patients. In addition, opportunistic infection due to Burkholderia cepacia complex can occur, especially through transmission from patient to patient. In addition to typical bacterial infections, people with CF more commonly develop other types of lung diseases. Among these is allergic bronchopulmonary aspergillosis, in which the body's response to the common fungus Aspergillus fumigatus causes worsening of breathing problems. Another is infection with Mycobacterium avium complex, a group of bacteria related to tuberculosis, which can cause lung damage and do not respond to common antibiotics. The mucus in the paranasal sinuses is equally thick and may also cause blockage of the sinus passages, leading to infection. This may cause facial pain, fever, nasal drainage, and headaches. Individuals with CF may develop overgrowth of the nasal tissue (nasal polyps) due to inflammation from chronic sinus infections. Recurrent sinonasal polyps can occur in 10% to 25% of CF patients. These polyps can block the nasal passages and increase breathing difficulties. Cardiorespiratory complications are the most common causes of death (about 30%) among patients at CF centers in the United States.
Gastrointestinal Digestive problems are also prevalent in individuals with CF. Approximately 15–20% of newborns diagnosed with CF experience intestinal blockage (meconium ileus), and other digestive issues may arise due to mucus accumulation in the pancreas. Consequently, there is impaired insulin production, leading to cystic fibrosis-related diabetes mellitus. Moreover, enzyme transport disruption from the pancreas to the intestines results in digestive problems such as recurrent diarrhea or weight loss. In cystic fibrosis, there is impaired chloride secretion due to the mutation of CFTR. This disrupts the ionic balance, causes impaired bicarbonate secretion, and alters the pH. The pancreatic enzymes that work in a specific pH range cannot act as the chyme is not neutralized by bicarbonate ions. This causes impairment of the digestion process. The thick mucus seen in the lungs has a counterpart in thickened secretions from the pancreas, an organ responsible for providing digestive juices that help break down food. These secretions block the exocrine movement of the digestive enzymes into the duodenum and result in irreversible damage to the pancreas, often with painful inflammation (pancreatitis). The pancreatic ducts are totally plugged in more advanced cases, usually seen in older children or adolescents. This causes atrophy of the exocrine glands and progressive fibrosis. In addition, protrusion of internal rectal membranes (rectal prolapse) is more common, occurring in as many as 10% of children with CF, and it is caused by increased fecal volume, malnutrition, and increased intra–abdominal pressure due to coughing. Individuals with CF also have difficulties absorbing the fat-soluble vitamins A, D, E, and K. In addition to the pancreas problems, people with CF experience more heartburn, intestinal blockage by intussusception, and constipation. Older individuals with CF may develop distal intestinal obstruction syndrome, which occurs when feces becomes thick with mucus (inspissated) and can cause bloating, pain, and incomplete or complete bowel obstruction. Exocrine pancreatic insufficiency occurs in the majority (85–90%) of patients with CF. It is mainly associated with "severe" CFTR mutations, where both alleles are completely nonfunctional (e.g. ΔF508). It occurs in 10–15% of patients with one "severe" and one "mild" CFTR mutation where little CFTR activity still occurs, or where two "mild" CFTR mutations exist. In these milder cases, a sufficient pancreatic exocrine function is still present so enzyme supplementation is not required. Usually, no other GI complications occur in pancreas-sufficient phenotypes, and in general, such individuals usually have excellent growth and development. Despite this, idiopathic chronic pancreatitis can occur in a subset of pancreas-sufficient individuals with CF, and is associated with recurrent abdominal pain and life-threatening complications. Liver diseases are another common complication in CF patients. The prevalence in studies ranged from 18% at age two to 41% at age 12, with no significant increase thereafter. Another study found that males with CF are more prone to liver diseases compared to females, and those with meconium ileus have an increased risk of liver diseases. Thickened secretions also may cause liver problems in patients with CF. Bile secreted by the liver to aid in digestion may block the bile ducts, leading to liver damage. Impaired digestion or absorption of lipids can result in steatorrhea. Over time, this can lead to scarring and nodularity (cirrhosis). The liver fails to rid the blood of toxins and does not make important proteins, such as those responsible for blood clotting. Around 5–7% of people experience liver damage severe enough to cause symptoms: typically gallstones causing biliary colic.
Endocrine The pancreas contains the islets of Langerhans, which are responsible for making insulin, a hormone that helps regulate blood glucose. Damage to the pancreas can lead to loss of the islet cells, leading to a type of diabetes unique to those with the disease. This cystic fibrosis-related diabetes shares characteristics of type 1 and type 2 diabetes, and is one of the principal nonpulmonary complications of CF. Vitamin D is involved in calcium and phosphate regulation. Poor uptake of vitamin D from the diet because of malabsorption can lead to the bone disease osteoporosis in which weakened bones are more susceptible to fractures.
Infertility Infertility affects both men and women. At least 97% of men with cystic fibrosis are infertile, but not sterile, and can have children with assisted reproductive techniques. The main cause of infertility in men with cystic fibrosis is congenital absence of the vas deferens (which normally connects the testes to the ejaculatory ducts of the penis), but potentially also by other mechanisms causing no sperm, abnormally shaped sperm, and few sperm with poor motility. Many men found to have congenital absence of the vas deferens during evaluation for infertility have a mild, previously undiagnosed form of CF. While females with CF are generally fertile, around 20% of women with CF have fertility difficulties due to thickened cervical mucus or malnutrition. In severe cases, malnutrition disrupts ovulation and causes a lack of menstruation.
Causes
CF is caused by having no functional copies (alleles) of the cystic fibrosis transmembrane conductance regulator gene CFTR. As of 2018, over 1,900 mutations leading to CF have been described, but only 5 of them have a frequency greater than 1% among patients. The most common mutant allele, ΔF508 (also termed F508del), is a deletion (Δ signifying deletion) of three nucleotides that results in a loss of the amino-acid residue phenylalanine (F) at the 508th position of the protein. This mutant allele is already present in 1 in 20 to 25 people of Northern European ancestry; it accounts for 70% of CF cases worldwide and 90% of cases in the United States; however, over 700 other mutant alleles, some of which represent new mutations, can produce CF. Although most people have two working copies (alleles) of the CFTR gene, only one is needed to prevent cystic fibrosis. CF develops when neither allele can produce a functional CFTR protein. Thus, CF is considered an autosomal recessive disease. The CFTR gene, found at the q31.2 locus of chromosome 7, is 230,000 base pairs long, and encodes a protein that is 1,480 amino acids long. More specifically, the location is between base pair 117,120,016 and 117,308,718 on the long arm of chromosome 7, region 3, band 1, subband 2, represented as 7q31.2. Structurally, the CFTR is a type of gene known as an ABC gene. The product of this gene (the CFTR protein) is a chloride ion channel important in creating sweat, digestive juices, and mucus. This protein possesses two ATP-hydrolyzing domains, which allows the protein to use energy in the form of ATP. It also contains two domains comprising six alpha helices apiece, which allow the protein to cross the cell membrane. A regulatory binding site on the protein allows activation by phosphorylation, mainly by cAMP-dependent protein kinase. The carboxyl terminal of the protein is anchored to the cytoskeleton by a PDZ domain interaction. Most CFTR in lung passages is produced by rare ion-transporting cells that regulate mucus properties. In addition, the evidence is increasing that genetic modifiers besides CFTR modulate the frequency and severity of the disease. One example is mannan-binding lectin, which is involved in innate immunity by facilitating phagocytosis of microorganisms. Polymorphisms in one or both mannan-binding lectin alleles that result in lower circulating levels of the protein are associated with a threefold higher risk of end-stage lung disease, as well as an increased burden of chronic bacterial infections.
Carriers Up to one in 25 individuals of Northern European ancestry is considered a genetic carrier. The disease appears only when two of these carriers have children, as each pregnancy between them has a 25% chance of producing a child with the disease. Although only about one of every 3,000 newborns of the affected ancestry has CF, since the CFTR gene's discovery in 1989, over 2,000 variants have been identified, but only about 700 of these have been recognized as responsible for causing CF. Current tests look for the most common mutations. The mutant alleles screened by the test vary according to a person's ethnic group or by the occurrence of CF already in the family. More than 10 million Americans, including one in 25 white Americans, are carriers of one mutant allele of the CF gene. CF is present in other races, though not as frequently as in white individuals. About one in 46 Hispanic Americans, one in 65 African Americans, and one in 90 Asian Americans carry a mutation of the CF gene.
Pathophysiology
The CFTR gene regulates the transport of salts and water through cell membranes, providing instructions for creating a pathway that allows the passage of chloride ions. A mutation in the CFTR gene can impair the normal function of chloride channels, leading to abnormal transport of chloride ions and water, resulting in the formation of thick and abnormal mucus. In the pancreatic duct, chloride transport occurs through the voltage-gated chloride channels influenced by CFTR (Cystic Fibrosis transmembrane conductance regulator). These channels are localised in the apical membrane of epithelial cells in the pancreatic duct. Several mutations in the CFTR gene can occur, and different mutations cause different defects in the CFTR protein, sometimes causing a milder or more severe disease. These protein defects are also targets for drugs which can sometimes restore their function. ΔF508-CFTR gene mutation, which occurs in >90% of patients in the U.S., creates a protein that does not fold normally and is not appropriately transported to the cell membrane, resulting in its degradation. Other mutations result in proteins that are too short (truncated) because production is ended prematurely. Other mutations produce proteins that do not use energy (in the form of ATP) normally, do not allow chloride, iodide, and thiocyanate to cross the membrane appropriately, and degrade faster than normal. Mutations may also lead to fewer copies of the CFTR protein being produced. The protein created by this gene is anchored to the outer membrane of cells in the sweat glands, lungs, pancreas, and all other remaining exocrine glands in the body. The protein spans this membrane and acts as a channel connecting the inner part of the cell (cytoplasm) to the surrounding fluid. This channel is primarily responsible for controlling the movement of halide anions from inside to outside of the cell; however, in the sweat ducts, it facilitates the movement of chloride from the sweat duct into the cytoplasm. When the CFTR protein does not resorb ions in sweat ducts, chloride, and thiocyanate released from sweat glands are trapped inside the ducts and pumped to the skin. When CFTR function is impaired in the sweat ducts, chloride reabsorption is reduced, resulting in abnormally high concentrations of chloride (and secondarily sodium) in sweat, which forms the basis of the diagnostic sweat chloride test. Additionally, hypothiocyanite (OSCN−) cannot be produced by the immune defense system. Because chloride is negatively charged, this modifies the electrical potential inside and outside the cell that normally causes cations to cross into the cell. Sodium is the most common cation in the extracellular space. The excess chloride within sweat ducts prevents sodium resorption by epithelial sodium channels and the combination of sodium and chloride creates the salt, which is lost in high amounts in the sweat of individuals with CF. This lost salt forms the basis for the sweat test. Most of the damage in CF is due to blockage of the narrow passages of affected organs with thickened secretions. These blockages lead to remodeling and infection in the lung, damage by accumulated digestive enzymes in the pancreas, blockage of the intestines by thick feces, etc. Several theories have been posited on how the defects in the protein and cellular function cause the clinical effects. The current theory suggests that defective ion transport leads to dehydration in the airway epithelia, thickening mucus. In airway epithelial cells, the cilia exist in between the cell's apical surface and mucus in a layer known as airway surface liquid (ASL). The flow of ions from the cell and into this layer is determined by ion channels such as CFTR. CFTR allows chloride ions to be drawn from the cell and into the ASL, but it also regulates another channel called ENac, which allows sodium ions to leave the ASL and enter the respiratory epithelium. CFTR normally inhibits this channel, but if the CFTR is defective, then sodium flows freely from the ASL and into the cell. As water follows sodium, the depth of ASL will be depleted and the cilia will be left in the mucous layer. As cilia cannot effectively move in a thick, viscous environment, mucociliary clearance is deficient and a buildup of mucus occurs, clogging small airways. The accumulation of more viscous, nutrient-rich mucus in the lungs allows bacteria to hide from the body's immune system, causing repeated respiratory infections. The presence of the same CFTR proteins causes mucous plugging and obstruction pathologies in other organs. In the pancreas, obstruction of the pancreatic duct inhibits secretion of bicarbonate and pancreatic enzymes into the duodenum. The pH of chyme entering the small intestine is not effectively neutralized, degrading what pancreatic enzymes do reach the intestines. Fat in the chyme goes unprocessed, and poor absorption of fat-soluble vitamins results. Obstruction of the biliary tract results in gallstones for up to 15% of CF patients. Increased pressure in the hepatic portal vein can lead to splenomegaly. Increased fluid absorption in the intestinal tract leads to constipation and, in infants, meconium ileus. In sweat glands, the flow of chloride through CFTR channels is reversed compared to other affected organs. In CF, chloride cannot be absorbed back into the body through sweat gland tissues, causing a buildup of chloride in sweat, salty skin, fluid loss, and in severe cases, hyponatremic dehydration.
Chronic infections The lungs of individuals with cystic fibrosis are colonized and infected by bacteria from an early age. These bacteria, which often spread among individuals with CF, thrive in the altered mucus, which collects in the small airways of the lungs. This mucus leads to the formation of bacterial microenvironments known as biofilms that are difficult for immune cells and antibiotics to penetrate. Viscous secretions and persistent respiratory infections repeatedly damage the lungs by gradually remodeling the airways, which makes infection even more difficult to eradicate. The natural history of CF lung infections and airway remodeling is poorly understood, largely due to the immense spatial and temporal heterogeneity both within and between the microbiomes of CF patients. Over time, the types of bacteria and their characteristics change in individuals with CF. In the initial stage, common bacteria such as S. aureus and H. influenzae colonize and infect the lungs. Eventually, Pseudomonas aeruginosa (and sometimes Burkholderia cepacia) dominates. By 18 years of age, 80% of patients with classic CF harbor P. aeruginosa, and 3.5% harbor B. cepacia. Once within the lungs, these bacteria adapt to the environment and develop resistance to commonly used antibiotics. Pseudomonas can develop special characteristics that allow the formation of large colonies, known as "mucoid" Pseudomonas, which are rarely seen in people who do not have CF. Scientific evidence suggests the interleukin 17 pathway plays a key role in resistance and modulation of the inflammatory response during P. aeruginosa infection in CF. In particular, interleukin 17-mediated immunity plays a double-edged activity during chronic airways infection; on one side, it contributes to the control of P. aeruginosa burden, while on the other, it propagates exacerbated pulmonary neutrophilia and tissue remodeling. Infection can spread by passing between different individuals with CF. In the past, people with CF often participated in summer "CF camps" and other recreational gatherings. Hospitals grouped patients with CF into common areas and routine equipment (such as nebulizers) was not sterilized between individual patients. This led to the transmission of more dangerous strains of bacteria among groups of patients. As a result, individuals with CF are now routinely isolated from one another in the healthcare setting, and healthcare providers are encouraged to wear gowns and gloves when examining patients with CF to limit the spread of virulent bacterial strains. CF patients may also have their airways chronically colonized by filamentous fungi (such as Aspergillus fumigatus, Scedosporium apiospermum, Aspergillus terreus) and/or yeasts (such as Candida albicans); other filamentous fungi less commonly isolated include Aspergillus flavus and Aspergillus nidulans (occur transiently in CF respiratory secretions) and Exophiala dermatitidis and Scedosporium prolificans (chronic airway-colonizers); some filamentous fungi such as Penicillium emersonii and Acrophialophora fusispora are encountered in patients almost exclusively in the context of CF. Defective mucociliary clearance characterizing CF is associated with local immunological disorders. In addition, prolonged therapy with antibiotics and corticosteroid treatments may also facilitate fungal growth. Although the clinical relevance of the fungal airway colonization is still a matter of debate, filamentous fungi may contribute to the local inflammatory response and therefore to the progressive deterioration of the lung function, as often happens with allergic bronchopulmonary aspergillosis – the most common fungal disease in the context of CF, involving a Th2-driven immune response to Aspergillus species.
Diagnosis
Diagnosis of cystic fibrosis is initially based on clinical findings indicative of respiratory, gastrointestinal, and/or genitourinary disease. Generally, definitive diagnosis of CF requires the presence of typical clinical features, a history of CF in a sibling, or a positive newborn screen, in addition to laboratory evidence of CFTR dysfunction. Laboratory evidence may consist of two elevated sweat chloride concentrations (>60 mmol/L) obtained on separate days, identification of two pathogenic genetic variants, or an abnormal nasal potential difference measurement. In many localities all newborns are screened for cystic fibrosis within the first few days of life, typically by blood test for high levels of immunoreactive trypsinogen. By 2010 every US state had instituted newborn screening programs and as of 2016, 21 European countries had programs in at least some regions. Immunoreactive trypsinogen (IRT) levels can be increased in individuals who have a single mutated copy of the CFTR gene (carriers) or, in rare instances, in individuals with two normal copies of the CFTR gene. Because IRT levels can fluctuate over time, newborn screening programs often use percentile-based cutoffs (e.g., IRT levels >95th percentile). Due to false positives, CF screening in newborns can be controversial. Of note, a positive screen identifies newborns with a high-likelihood of having CF, but an elevated IRT alone can not establish a diagnosis. Newborns with positive tests or those who are otherwise suspected of having cystic fibrosis based on symptoms or family history, then undergo a sweat test. An electric current is used to drive pilocarpine into the skin, stimulating sweating. The sweat is collected and analyzed for salt levels. Having unusually high levels of chloride in the sweat (>60 mmol/L) suggests CFTR is dysfunctional; the person is then diagnosed with cystic fibrosis. In contrast, a sweat chloride concentration <30 mmol/L makes the diagnosis of CF unlikely. In many cases, a parent initially suspects the diagnosis because the infant's skin tastes salty. Genetic testing is also available to identify the CFTR mutations typically associated with cystic fibrosis. Many laboratories can test for the 30–96 most common CFTR mutations, which can identify over 90% of people with cystic fibrosis. People with CF also have less thiocyanate and hypothiocyanite in their saliva and mucus. In the case of milder forms of CF, transepithelial potential difference measurements can be helpful. In patients with an equivocal or normal sweat chloride test, diagnosis may be supported by nasal potential difference testing, in which an increased voltage response to topical amiloride on the nasal epithelium is followed by absent or reduced voltage response to a beta-adrenergic agonist.
Prenatal Women who are pregnant or couples planning a pregnancy can have themselves tested for the CFTR gene mutations to determine the risk that their child will be born with CF. Testing is typically performed first on one or both parents and, if the risk of CF is high, testing on the fetus is performed. The American College of Obstetricians and Gynecologists recommends all people thinking of becoming pregnant be tested to see if they are a carrier. Because the development of CF in the fetus requires each parent to pass on a mutated copy of the CFTR gene and because CF testing is expensive, testing is often performed initially on one parent. If testing shows that the parent is a CFTR gene mutation carrier, the other parent is tested to calculate the risk that their children will have CF. CF can result from more than a thousand different mutations. As of 2016, typically only the most common mutations are tested for, such as ΔF508. Most commercially available tests look for 32 or fewer different mutations. If a family has a known uncommon mutation, specific screening for that mutation can be performed. Because not all known mutations are found on current tests, a negative screen does not guarantee that a child will not have CF. During pregnancy, testing can be performed on the placenta (chorionic villus sampling) or the fluid around the fetus (amniocentesis). However, chorionic villus sampling has a risk of fetal death of one in 100 and amniocentesis of one in 200; a recent study has indicated this may be much lower, about one in 1,600. Economically, for carrier couples of cystic fibrosis, when comparing preimplantation genetic diagnosis (PGD) with natural conception (NC) followed by prenatal testing and abortion of affected pregnancies, PGD provides net economic benefits up to a maternal age around 40 years, after which NC, prenatal testing, and abortion have a higher economic benefit.
Management Treatment for CF is diverse, tailored to different symptoms, and includes various devices, inhalation medications to alleviate respiratory difficulties, oral enzyme supplements to address exocrine pancreatic insufficiency, and, in some cases, surgical interventions for conditions such as meconium ileus. While treatment alleviates symptoms and prevents potential complications, there is currently no cure for the disease. The management of CF has improved significantly over the past 70 years. While infants born with it 70 years ago would have been unlikely to live beyond their first year, infants today are likely to live well into adulthood. Advances in the treatment of cystic fibrosis have meant that people with cystic fibrosis can live a fuller life less encumbered by their condition. The cornerstones of management are the proactive treatment of airway infection, encouragement of good nutrition, and an active lifestyle. Pulmonary rehabilitation as a management of CF continues throughout a person's life, and is aimed at maximizing organ function, and therefore the quality of life. Occupational therapists use energy conservation techniques in the rehabilitation process for patients with cystic fibrosis. Examples of energy conservation techniques are ergonomic principles, pursed lip breathing, and diaphragmatic breathing. People with CF tend to have fatigue and dyspnoea due to chronic pulmonary infections, so reducing the amount of energy spent during activities can help people feel better and gain more independence. At best, current treatments delay the decline in organ function. Because of the wide variation in disease symptoms, treatment typically occurs at specialist multidisciplinary centers and is tailored to the individual. Targets for therapy are the lungs, gastrointestinal tract (including pancreatic enzyme supplements), the reproductive organs (including assisted reproductive technology), and psychological support. The most consistent aspect of therapy in CF is limiting and treating the lung damage caused by thick mucus and infection, with the goal of maintaining quality of life. Intravenous, inhaled, and oral antibiotics are used to treat chronic and acute infections. Mechanical devices and inhalation medications are used to alter and clear the thickened mucus. These therapies, while effective, can be extremely time-consuming. Oxygen therapy at home is recommended in those with significantly low oxygen levels. Many people with CF use probiotics, which are thought to be able to correct intestinal dysbiosis and inflammation, but the clinical trial evidence regarding the effectiveness of probiotics for reducing pulmonary exacerbations in people with CF is uncertain.
Antibiotics Many people with CF are on one or more antibiotics at all times, even when healthy, to prophylactically suppress infection. The choice of antibiotics for cystic fibrosis depends on the specific bacteria that are causing the infection, as well as the patient's age, weight, and other medical conditions. Antibiotics are necessary whenever pneumonia is suspected or a noticeable decline in lung function is seen, and are usually chosen based on the results of a sputum analysis and the person's past response. This prolonged therapy often necessitates hospitalization and insertion of a more permanent IV such as a peripherally inserted central catheter or Port-a-Cath. Inhaled therapy with antibiotics such as tobramycin, colistin, and aztreonam is often given for months at a time to improve lung function by impeding the growth of colonized bacteria. Inhaled antibiotic therapy helps lung function by fighting infection, but also has significant drawbacks such as development of antibiotic resistance, tinnitus, and changes in the voice. Inhaled levofloxacin may be used to treat Pseudomonas aeruginosa in people with cystic fibrosis who are infected. Antibiotics by mouth such as ciprofloxacin or azithromycin are given to help prevent infection or to control ongoing infection. The aminoglycoside antibiotics (e.g. tobramycin) used can cause hearing loss, damage to the balance system in the inner ear or kidney failure with long-term use. To prevent these side-effects, the amount of antibiotics in the blood is routinely measured and adjusted accordingly. Currently, no reliable clinical trial evidence shows the effectiveness of antibiotics for pulmonary exacerbations in people with cystic fibrosis and Burkholderia cepacia complex or for the use of antibiotics to treat nontuberculous mycobacteria in people with CF.
Pseudomonas aeruginosa The early management of Pseudomonas aeruginosa infection is usually suggested using nebulised antibiotics with or without oral antibiotics to remove the bacteria from the person's airways for some time. When choosing antibiotics to treat lung infections caused by Pseudomonas aeruginosa in people with cystic fibrosis, it is still unclear whether the choice of antibiotics should be based on the results of testing antibiotics separately (one at a time) or in combination with each other. It is also unclear if these treatment approaches for the Pseudomonas aeruginosa infection improve the person's quality of life or lifespan. The negative side effects of antibiotics for this infection are also poorly studied. Intravenous antibiotic therapy to treat Pseudomonas aeruginosa infections is not any better than antibiotics taken orally.
Methicillin-resistant Staphylococcus aureus Methicillin-resistant Staphylococcus aureus (MRSA) infections can be dangerous for people with cystic fibrosis and can worsen lung damage leading to more rapid decline. Early antibiotic treatment is standard; however, further research is needed to determine longer-term effects and benefits (3–6 months after the treatment or longer) and survival rates associated with different treatment options.
Antibiotic adjuvant therapy Factors related to antibiotic use, the chronicity of the disease, and the emergence of resistant bacteria demand more exploration for different strategies such as antibiotic adjuvant therapy. Antibiotic adjuvant therapy refers to therapeutic approaches that aim to improve the action of antibiotics such a pharmaceutical agents or supplements that impact the virulence of the bacterium or that change the susceptibility of the organism to the antibiotic so that the antibiotics are more effective. There is no strong evidence to recommend specific antibiotic adjuvant therapies such as β-carotene, nitric oxide, zinc supplements, or KB001-A.
CFTR modulators CFTR modulators are medications taken by mouth that target defects in the CFTR protein rather than only treating the downstream symptoms of cystic fibrosis. Eligibility for CFTR modulator therapy depends on a person’s CFTR genotype, because individual modulators are effective only for specific CFTR variants. As of 2024, approximately 90% of patients have variants that respond to an available CFTR modulator. Ivacaftor is a modulator first approved in 2012 for the treatment of CF due to several specific mutations responsive to ivacaftor-induced CFTR protein enhancement. It is a CFTR potentiator, meaning that it improves the function of CFTR protein present at the cell surface. Ivacaftor targets the pathogenic variant G551D (present in approximately 5% of CF patients) and improves lung function by about 10%. The first year it was on the market, the list price was over $300,000 per year in the United States. In July 2015, the U.S. Food and Drug Administration approved lumacaftor/ivacaftor. Whereas ivacaftor is a CFTR potentiator, lumacaftor is a CFTR corrector, which improves processing and trafficking of misfolded CFTR protein to the cell surface. In 2018, the FDA approved the combination drug ivacaftor/tezacaftor; the manufacturer announced a list price of $292,000 per year. Tezacaftor helps move the CFTR protein to the correct position on the cell surface, and is designed to treat people with the F508del mutation (present in approximately 90% of CF patients). In 2019, the combination drug elexacaftor/tezacaftor/ivacaftor, marketed as Trikafta, was approved for CF patients over the age of 12 in the United States, with approval extended to children aged 6 years and older in 2021. In Europe, this drug was approved in 2020 and marketed as Kaftrio. It is used in those who have at least one F508del mutation. According to the Cystic Fibrosis Foundation, "this medicine represents the single greatest therapeutic advancement in the history of CF, offering a treatment for the underlying cause of the disease that could eventually bring modulator therapy to 90 percent of people with CF." In a clinical trial, participants who received the combination drug experienced a subsequent 63% decrease in pulmonary exacerbations and a 41.8 mmol/L decrease in sweat chloride concentration. Other studies have found substantial improvements in lung function, weight gain, and reductions in respiratory symptoms such as cough and sputum production. Treatment has also been associated with reduced school or work absenteeism as well as fewer hospitalizations. By mitigating a repertoire of symptoms associated with CF, the combination drug significantly improves quality-of-life metrics. The combination drug is also known to interact with CYP3A inducers, such as carbamazepine used in the treatment of bipolar disorder, causing elexacaftor/tezacaftor/ivacaftor to circulate in the body at decreased concentrations. As such, concurrent use is not recommended. The combination drug vanzacaftor/tezacaftor/deutivacaftor (Alyftrek) was approved for medical use in the United States in 2024. The list price of CFTR modulators has been reported to exceed