Cystic Fibrosis

Definition:
Cystic fibrosis (CF), or mucoviscoidosis, is a hereditary disease that affects mainly the lungs and digestive system, causing progressive disability.

Thick mucus production, as well as a less competent immune system, results in frequent lung infections. Diminished secretion of pancreatic enzymes is the main cause of poor growth, fatty diarrhea and deficiency in fat-soluble vitamins. Males can be infertile due to the condition congenital bilateral absence of the vas deferens. Often, symptoms of CF appear in infancy and childhood. Meconium ileus is a typical finding in newborn babies with CF.

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Individuals with cystic fibrosis can be diagnosed prior to birth by genetic testing. Newborn screening tests are increasingly common and effective. The diagnosis of CF is confirmed if high levels of salt are found during a sweat test.

There is no cure for CF, and most individuals with cystic fibrosis die young: many in their 20s and 30s from lung failure. However, with the continuous introduction of many new treatments, the life expectancy of a person with CF is increasing. Lung transplantation is often necessary as CF worsens.

Cystic fibrosis is one of the most common life-shortening, childhood-onset inherited diseases. In the United States, 1 in 3900 children are born with CF. It is most common among Europeans and Ashkenazi Jews; one in twenty-two people of European descent carry one gene for CF, making it the most common genetic disease in these populations.

Cystic fibrosis is the most common severe inherited disease in people of north american and european origin. The condition is much rare in other ethnic groups. for example, in the us, about 1 in 2,500 white babies has the disorder compared with 1 in 17,000 african-american babies. All the fluids and mucus-secreting glands in the body are affected and this leads to thick, abnormal secretions, especially in the lungs and pancreas. As a result, children who are affected may experience recurrent chest infections and have problems absorbing nutrients from food.

CF is caused by a mutation in a gene called the cystic fibrosis transmembrane conductance regulator (CFTR). The product of this gene is a chloride ion channel important in creating sweat, digestive juices, and mucus. Although most people without CF have two working copies of the CFTR gene, only one is needed to prevent cystic fibrosis. CF develops when neither gene works normally. Therefore, CF is considered an autosomal recessive disease.

In the past, severe chest infections were a major cause of deaths in children with cystic fibrosis. Today, with better understanding of the disease and recent advances in treatment, most affected children survive into adulthood.

Causes:
Cystic fibrosis is caused by an abnormal gene, which is carried by about 1 in 25 people and inherited in an autosomal recessive manner. The abnormal gene occurs on chromosome number 7. over 300 different mutations (abnormalities) in the gene have now been identified. Of these, the most common is called delta 508, and this is the cause of more than 1 in 7 cases of cystic fibrosis in the us.

Symptoms:
Sometimes, a newborn baby with cystic fibrosis may have a swollen abdomen and does not pass feces for the first few days after birth. other symptoms of cystic fibrosis usually develop later in infancy and may include:

· Failure to put on weight or grow at the normal rate.
· Pale, greasy feces that float and have a particularly offensive smell.
· Recurrent chest infections.

In many cases of cystic fibrosis, a constant cough develops, producing large amounts of sticky mucus.

Lung and sinus disease:
Lung disease results from clogging of airways due to inflammation. Inflammation and infection cause injury to the lungs and structural changes that lead to a variety of symptoms. In the early stages, incessant coughing, copious phlegm production, and decreased ability to exercise are common. Many of these symptoms occur when bacteria that normally inhabit the thick mucus grow out of control and cause pneumonia. In later stages of CF, changes in the architecture of the lung further exacerbate chronic difficulties in breathing.

Other symptoms include coughing up blood (hemoptysis), changes in the major airways in the lungs (bronchiectasis), high blood pressure in the lung (pulmonary hypertension), heart failure, difficulties getting enough oxygen to the body, and respiratory failure requiring support with breathing masks such as bilevel positive airway pressure machines or ventilators. In addition to typical bacterial infections, people with CF more commonly develop other types of lung disease. 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 (MAC), a group of bacteria related to tuberculosis, which can cause further lung damage and does not respond to common antibiotics.

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. These polyps can block the nasal passages and increase breathing difficulties.

Gastrointestinal, liver and pancreatic disease:
Prior to prenatal and newborn screening, cystic fibrosis was often diagnosed when a newborn infant failed to pass faeces (meconium). Meconium may completely block the intestines and cause serious illness. This condition, called meconium ileus, occurs in 10% of newborns with CF. In addition, protrusion of internal rectal membranes (rectal prolapse) is more common in CF because of increased fecal volume, malnutrition, and increased intra–abdominal pressure due to coughing.

The thick mucus seen in the lungs has its counterpart in thickened secretions from the pancreas, an organ responsible for providing digestive juices which help break down food. These secretions block the movement of the digestive enzymes into the duodenum and result in irreversible damage to the pancreas, often with painful inflammation (pancreatitis). The lack of digestive enzymes leads to difficulty absorbing nutrients with their subsequent excretion in the faeces, a disorder known as malabsorption. Malabsorption leads to malnutrition and poor growth and development because of calorie loss. Individuals with CF also have difficulties absorbing the fat-soluble vitamins A, D, E, and K. In addition to the pancreas problems, people with cystic fibrosis experience more heartburn, intestinal blockage by intussusception, and constipation.[8] Older individuals with CF may also develop distal intestinal obstruction syndrome when thickened faeces cause intestinal blockage.

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. Over time, this can lead to cirrhosis, in which the liver fails to rid the blood of toxins and does not make important proteins such as those responsible for blood clotting.

Endocrine disease and growth:

The pancreas contains the islets of Langerhans, which are responsible for making insulin, a hormone that helps regulate blood glucose. Damage of the pancreas can lead to loss of the islet cells, leading to diabetes that is unique to those with the disease. Cystic Fibrosis Related Diabetes (CFRD), as it is known as, shares characteristics that can be found in Type 1 and Type 2 diabetics and is one of the principal non-pulmonary complications of CF. Vitamin D is involved in calcium and phosphorus regulation. Poor uptake of vitamin D from the diet because of malabsorption leads to the bone disease osteoporosis in which weakened bones are more susceptible to fractures.[13] In addition, people with CF often develop clubbing of their fingers and toes due to the effects of chronic illness and low oxygen on their tissues.

Poor growth is a hallmark of CF. Children with CF typically do not gain weight or height at the same rate as their peers, and occasionally are not diagnosed until investigation is initiated for poor growth. The causes of growth failure are multi–factorial and include chronic lung infection, poor absorption of nutrients through the gastrointestinal tract, and increased metabolic demand due to chronic illness.

Infertility :
Infertility affects both men and women. At least 97 percent of men with cystic fibrosis are infertile. These men make normal sperm but are missing the tube (vas deferens), which connects the testes to the ejaculatory ducts of the penis. Many men found to have congenital absence of the vas deferens during evaluation for infertility have a mild, previously undiagnosed form of CF. Some women have fertility difficulties due to thickened cervical mucus or malnutrition. In severe cases, malnutrition disrupts ovulation and causes amenorrhea.

Diagnosis and monitoring :
Cystic fibrosis may be diagnosed by many different categories of testing including those such as, newborn screening, sweat testing, or genetic testing. As of 2006 in the United States, 10percent of cases are diagnosed shortly after birth as part of newborn screening programs. The newborn screen initially measures for raised blood concentration of immunoreactive trypsinogen. However, most states and countries do not screen for CF routinely at birth. Therefore, most individuals are diagnosed after symptoms prompt an evaluation for cystic fibrosis. The most commonly-used form of testing is the sweat test. Sweat-testing involves application of a medication that stimulates sweating (pilocarpine) to one electrode of an apparatus and running electric current to a separate electrode on the skin. This process, called iontophoresis, causes sweating; the sweat is then collected on filter paper or in a capillary tube and analyzed for abnormal amounts of sodium and chloride. People with CF have increased amounts of sodium and chloride in their sweat. CF can also be diagnosed by identification of mutations in the CFTR gene.

A multitude of tests is used to identify complications of CF and to monitor disease progression. X-rays and CAT scans are used to examine the lungs for signs of damage or infection. Examination of the sputum under a microscope is used to identify which bacteria are causing infection so that effective antibiotics can be given. Pulmonary function tests measure how well the lungs are functioning, and are used to measure the need for and response to antibiotic therapy. Blood tests can identify liver problems, vitamin deficiencies, and the onset of diabetes. DEXA scans can screen for osteoporosis and testing for fecal elastase can help diagnose insufficient digestive enzymes.

Prenatal diagnosis:
Couples who are pregnant or who are planning a pregnancy can themselves be tested for CFTR gene mutations to determine the likelihood that their child will be born with cystic fibrosis. Testing is typically performed first on one or both parents and, if the risk of CF is found to be high, testing on the fetus can then be performed. Cystic fibrosis testing is offered to many couples in the US. The American College of Obstetricians and Gynecologists (ACOG) recommends testing for couples who have a personal or close family history. Additionally, ACOG recommends that carrier testing be offered to all Caucasian couples and be made available to couples of other ethnic backgrounds.

Because 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 on just one parent initially. If that parent is found to be a carrier of a CFTR gene mutation, the other parent is then tested to calculate the risk that their children will have CF. CF can result from more than a thousand different mutations and, as of 2006, it is not possible to test for each one. Testing analyzes the blood for the most common mutations 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. In addition, because the mutations tested are necessarily those most common in the highest risk groups, testing in lower risk ethnicities is less successful because the mutations commonly seen in these groups are less common in the general population. These couples may therefore consider testing through labs that offer CF screens with a high number of mutations tested.

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Couples who are at high risk for having a child with CF will often opt to perform further testing before or during pregnancy. In vitro fertilization with preimplantation genetic diagnosis offers the possibility to examine the embryo prior to its placement into the uterus. The test, performed 3 days after fertilization, looks for the presence of abnormal CF genes. If two mutated CFTR genes are identified, the embryo is not used for embryo transfer and an embryo with at least one normal gene is implanted.

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 1 in 100 and amniocentesis of 1 in 200, so the benefits must be determined to outweigh these risks prior to going forward with testing. Alternatively, some couples choose to undergo third party reproduction with egg or sperm.

Treatment:
Treatment for cystic fibrosis is aimed at slowing the progression of lung disease and maintaining adequate nutrition.

Chest physical therapy is usually performed twice a day to remove secretions from the lungs. Parents and older affected children are often taught how to do this procedure at home. If an affected child develops a chest infection, he or she will require immediate treatment with antibiotics. in addition, long-term use of antibiotics may be necessary to prevent other chest infections from developing. older children sometimes require regular courses of intravenous antibiotics to treat bacteria that become established in the lung secretions. In this case, under general anesthesia, a permanent catheter may be inserted under the chest wall so that the antibiotics can be administered more easily. some affected children are helped by inhaled drugs that reduce the stickiness of the secretions. In some cases, it may be possible to carry out a heart-lung transplant if the lungs are severely damaged and suitable organs become available.

A high-calorie diet helps ensure that a child with cystic fibrosis grows normally. he or she may also need to take pancreatic enzymes and vitamin supplements with every meal.

An affected child and his or her family will receive psychological support, particularly during adolescence when chronic illness is especially difficult to cope with. family members may find it helpful to join a support group.

The cornerstones of management are proactive treatment of airway infection, and encouragement of good nutrition and an active lifestyle. The treatment for cystic fibrosis continues throughout a patient’s life, and is aimed at maximising organ function, and therefore quality of life. At best, current treatments delay the decline in organ function. Treatment typically occurs at specialist multidisciplinary centres, and is tailored to the individual, because of the wide variation in disease symptoms. Targets for therapy are the lungs, gastrointestinal tract (including insulin treatment), the reproductive organs (including Assisted Reproductive Technology (ART)) and psychological support. In addition, therapies such as transplantation and gene therapy aim to cure some of the effects of cystic fibrosis.

The most consistent aspect of therapy in cystic fibrosis 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.

Antibiotics to treat lung disease:
Antibiotics are given whenever pneumonia is suspected or there has been a decline in lung function. Antibiotics are often chosen based on information about prior infections. Many bacteria common in cystic fibrosis are resistant to multiple antibiotics and require weeks of treatment with intravenous antibiotics such as vancomycin, tobramycin, meropenem, ciprofloxacin, and piperacillin. This prolonged therapy often necessitates hospitalization and insertion of a more permanent IV such as a PICC line or Port-a-Cath. Inhaled therapy with antibiotics such as tobramycin and colistin is often given for months at a time in order to improve lung function by impeding the growth of colonized bacteria.Oral antibiotics such as ciprofloxacin or azithromycin are sometimes given to help prevent infection or to control ongoing infection. Some individuals spend years between hospitalizations for antibiotics, whereas others require several antibiotic treatments each year.

Several common antibiotics such as tobramycin and vancomycin can cause hearing loss or kidney problems with long-term use. In order to prevent these side-effects, the amount of antibiotics in the blood are routinely measured and adjusted accordingly.

Other methods to treat lung disease:
Several mechanical techniques are used to dislodge sputum and encourage its expectoration. In the hospital setting, physical therapy is utilized; a therapist pounds an individual’s chest with his or her hands several times a day. Devices that recreate this percussive therapy include the ThAIRapy Vest and the intrapulmonary percussive ventilator (IPV). Newer methods such as Biphasic Cuirass Ventilation, and associated clearance mode available in such devices, now integrate a cough assistance phase, as well as a vibration phase for dislodging secretions. Biphasic Cuirass Ventilation is also shown to provide a bridge to transplantation. These are portable and adapted for home use.[37] Aerobic exercise is of great benefit to people with cystic fibrosis. Not only does exercise increase sputum clearance but it also improves cardiovascular and overall health.

Aerosolized medications that help loosen secretions include dornase alfa and hypertonic saline. Dornase is a recombinant human deoxyribonuclease, which breaks down DNA in the sputum, thus decreasing its viscosity. N-Acetylcysteine may also decrease sputum viscosity, but research and experience have shown its benefits to be minimal. Albuterol and ipratropium bromide are inhaled to increase the size of the small airways by relaxing the surrounding muscles.

As lung disease worsens, breathing support from machines may become necessary. Individuals with CF may need to wear special masks at night that help push air into their lungs. These machines, known as bilevel positive airway pressure (BiPAP) ventilators, help prevent low blood oxygen levels during sleep. BiPAP may also be used during physical therapy to improve sputum clearance. During severe illness, people with CF may need to have a tube placed in their throats and their breathing supported by a ventilator.

Treatment of other aspects of CF:
Newborns with meconium ileus typically require surgery, whereas adults with distal intestinal obstruction syndrome typically do not. Treatment of pancreatic insufficiency by replacement of missing digestive enzymes allows the duodenum to properly absorb nutrients and vitamins that would otherwise be lost in the faeces. Even so, most individuals with CF take additional amounts of vitamins A, D, E, and K and eat high-calorie meals. It should be noted, however, that nutritional advice given to patients is, at best, mixed: Often, literature encourages the eating of high-fat foods without differentiating between saturated and unsaturated fats/trans-fats; this lack of clear information runs counter to health advice given to the general population, and creates the risk of further serious health problems for people with cystic fibrosis as they grow older. So far, no large-scale research involving the incidence of atherosclerosis and coronary heart disease in adults with cystic fibrosis has been conducted.

The diabetes common to many CF patients is typically treated with insulin injections or an insulin pump. Development of osteoporosis can be prevented by increased intake of vitamin D and calcium, and can be treated by bisphosphonates. Poor growth may be avoided by insertion of a feeding tube for increasing calories through supplemental feeds or by administration of injected growth hormone.

Sinus infections are treated by prolonged courses of antibiotics. The development of nasal polyps or other chronic changes within the nasal passages may severely limit airflow through the nose. Sinus surgery is often used to alleviate nasal obstruction and to limit further infections. Nasal steroids such as fluticasone are used to decrease nasal inflammation. Female infertility may be overcome by assisted reproduction technology, particularly embryo transfer techniques. Male infertility may be overcome with intracytoplasmic sperm injection.Third party reproduction is also a possibility for women with CF.

Transplantation and gene therapy:
Lung transplantation often becomes necessary for individuals with cystic fibrosis as lung function and exercise tolerance declines. Although single lung transplantation is possible in other diseases, individuals with CF must have both lungs replaced because the remaining lung would contain bacteria that could infect the transplanted lung. A pancreatic or liver transplant may be performed at the same time in order to alleviate liver disease and/or diabetes. Lung transplantation is considered when lung function approaches a point where it threatens survival or requires assistance from mechanical devices.

Gene therapy holds promise as a potential avenue to cure cystic fibrosis. Gene therapy attempts to place a normal copy of the CFTR gene into affected cells. Studies have shown that to prevent the lung manifestations of cystic fibrosis, only 5–10% the normal amount of CFTR gene expression is needed.[48] Many approaches have been theorized and several clinical trials have been initiated but, as of 2006, many hurdles still exist before gene therapy can be successful.

Prognosis:
In most cases, CF causes an early death. Average life expectancy is around 36.8 years, although improvements in treatments mean a baby born today could expect to live longer.

Epidemiology:
Cystic fibrosis is the most common life-limiting autosomal recessive disease among people of European heritage. In the United States, approximately 30,000 individuals have CF; most are diagnosed by six months of age. Canada has approximately 3,000 citizens with CF. Approximately 1 in 25 people of European descent and 1 in 22 people of Ashkenazi Jewish descent is a carrier of a cystic fibrosis mutation. Although CF is less common in these groups, approximately 1 in 46 Hispanics, 1 in 65 Africans and 1 in 90 Asians carry at least one abnormal CFTR gene.

Cystic fibrosis is diagnosed in males and females equally. For unclear reasons, males tend to have a longer life expectancy than females. Life expectancy for people with CF depends largely upon access to health care. In 1959, the median age of survival of children with cystic fibrosis was six months. In the United States, the life expectancy for infants born in 2006 with CF is 36.8 years, based upon data compiled by the Cystic Fibrosis Foundation. In developed countries, people with CF live to a similar age. However, the life expectancy in underdeveloped countries is much less: The majority of individuals with CF do not live past the age of 10.

The Cystic Fibrosis Foundation also compiles lifestyle information about American adults with CF. In 2004, the foundation reported that 91% had graduated high school and 54% had at least some college education. Employment data revealed 12.6% of adults were disabled and 9.9% were unemployed. Marital information showed that 59% of adults were single and 36% were married or living with a partner. In 2004, 191 American women with CF were pregnant.

Can it be prevented?
Genetic testing means that carriers can be identified and that the disorder can be detected prenatally. Genetic testing may be offered to adults with a family history of cystic fibrosis and partners of people who have the disease. If these tests results are positive, the couple will be offered genetic counseling. A couple at risk may pot to use assisted conception, which enables the embryo to be tested for the abnormal gene before it is implanted by in-vitro fertilization. pregnant women may be offered prenatal genetic tests.

In the future, cystic fibrosis may be treated with gene therapy, in which a normal gene is introduced into relevant tissues to prevent cystic fibrosis from developing. The results of research in this field are promising.

Disclaimer: This information is not meant to be a substitute for professional medical advise or help. It is always best to consult with a Physician about serious health concerns. This information is in no way intended to diagnose or prescribe remedies.This is purely for educational purpose

Resources:
http://en.wikipedia.org/wiki/Cystic_fibrosis
http://www.charak.com/DiseasePage.asp?thx=1&id=328

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