Cystic Fibrosis (CF), the most common life-limiting disease in Caucasians, is an autosomal recessive disease, which means that for an individual to have cystic fibrosis, he/she must inherit one cystic fibrosis mutation from each parent. Nearly 2000 cystic fibrosis mutations have been described. Cystic Fibrosis occurs in approximately 1 in 3,400 live births in the U.S. It affects approximately 30,000 people in the U.S. and 70,000 people worldwide. In the U.S., approximately 1 in 29 people carry one cystic fibrosis mutation. Survival in cystic fibrosis has improved dramatically. In the 1940s, most children with cystic fibrosis did not live to see their first birthday. Today the survival is approximately 40 years. For the first time in history there are now more adults with cystic fibrosis than children. While this is an impressive accomplishment, there is still much work to be done.
Cystic Fibrosis mutations cause an abnormality in a chloride channel, the cystic fibrosis transmembrane conductance regulator (CFTR), which is expressed on the surface of cells located in the lungs, sinuses, liver, pancreas, intestines, sweat glands, and reproductive organs. Because the channel is defective, chloride cannot move normally between the cell and its environment. This often causes the secretions in these organs to become thick and sticky, thus creating an obstruction. The lungs seem to be exquisitely sensitive to the abnormal movement of chloride. The airways in the lungs of a person with cystic fibrosis will become blocked by mucus. The mucus eventually becomes infected by bacteria which incite a strong inflammatory response. Instead of eliminating the bacteria, the inflammatory response actually damages the lungs and ultimately causes most of the morbidity and mortality of the disease. Treatment of cystic fibrosis lung disease involves the administration of chest physiotherapy, mucus thinners, and mucus hydrators to relieve the obstructed airways, antibiotics to treat the chronic bacterial infection, and anti-inflammatory drugs to reduce the exaggerated inflammatory response. Active clinical trials are ongoing in all of these areas.
People with cystic fibrosis also have issues with their gastrointestinal system. Most people with cystic fibrosis do not make adequate enzymes to digest food properly. Without treatment, they will not absorb essential fats, proteins, carbohydrates, vitamins, and minerals. This then leads to nutritional deficiencies and growth failure. In order to treat this, people with cystic fibrosis have to ingest enzyme capsules with each meal and snack and take extra vitamins. These therapies allow most people to gain weight and grow adequately.
Diagnosing cystic fibrosis early in life prior to the onset of permanent lung damage is imperative. Previously the diagnosis was not made until a child presented with symptoms, typically poor growth and nutrition and recurrent respiratory symptoms. Now, all 50 states have newborn screening programs in place for cystic fibrosis. This has significantly reduced the age of diagnosis. Newborn screening is confirmed by genetic testing and sweat chloride measurement. Since the advent of newborn screening, it is rare to see a baby with cystic fibrosis present with severe protein-calorie malnutrition that frequently occurred in the past. Early diagnosis is also important so that novel therapies that have been developed to correct the abnormal chloride channel can be initiated early in life. CFTR modulators that are specific for a patient’s mutations are just now becoming increasingly available. These modulators are known as potentiators and correctors. These drug increase the amount of functional CFTR on the surface of cells. One potentiator, ivacaftor, and one corrector, lumacaftor, are currently available to patients. These drugs have been associated with improved lung function, improved weight gain, decreased pulmonary exacerbations and decreased sweat chloride concentrations in clinical trials. There are many more potentiators and correctors being investigated in clinical trials and in the laboratories. In addition to potentiators and correctors, drugs that stabilize CFTR and amplify CFTR are also being evaluated in clinical trial. The hope is that specific CFTR modulators will be developed to address all cystic fibrosis mutations.
People with cystic fibrosis must take many medications and perform many therapies in order to maintain their health. These treatments must be done several times every day. It is not unusual for a person with cystic fibrosis to do therapies for more than 2 hours per day and swallow dozens of pills. This treatment burden significantly impacts a person’s quality of life. It is not uncommon for a person with cystic fibrosis to experience depression. We as healthcare providers are just now beginning to realize this, and we have recently begun screening for depression in our patients during clinical visits so that the appropriate treatment may be prescribed. However, as new therapies become available, it will be important for the cystic fibrosis community to determine what therapies are really pertinent to a given patient so that a health care provider can work with each patient to develop an individualized treatment plan. Reducing treatment burden while improving quality of life may ultimately have the greatest impact upon an individual’s mental health.
Four Facts About Cystic Fibrosis