Cystic Fibrosis

Thursday, September 25, 2008

Cystic fibrosis (CF) is an inherited disease of the exocrine glands of the lungs, liver, pancreas, and intestines, causing progressive disability due to multisystem failure. Normally, mucus is watery. It keeps the linings of certain organs moist and prevents them from drying out or getting infected. But in cystic fibrosis, an abnormal gene causes mucus to become thick and sticky. Thick mucus production 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.

Cystic fibrosis is one of the most common life-shortening, inherited diseases. In the United States, 1 in 3,900 children are born with CF. It is most common among Mediterranean populations and Ashkenazi Jews, as one in twenty-two people of Mediterranean descent are carriers of one gene for CF, making it the most common genetic disease in these populations. Ireland has the highest rate of cystic fibrosis carriers in the world, 1 in 19.

The thick, sticky mucus can also block tubes, or ducts, in your pancreas. As a result, digestive enzymes that are produced by your pancreas cannot reach your small intestine. These enzymes help break down the food that you eat. Without them, your intestines cannot absorb fats and proteins fully. As a result nutrients leave your body unused, and you can become malnourished, as you may not get enough vitamins A, D, E, and K. You may also have intestinal gas, a swollen belly, and pain or discomfort.

Lung disease results from clogging the airways due to mucus buildup and resulting 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. Respiratory failure is the most common cause of death in people with CF.

Infertility affects both men and women. At least 97 percent of men with cystic fibrosis are sterile. 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.

The abnormal gene also causes your sweat to become extremely salty. As a result, when you perspire, your body loses large amounts of salt. This can upset the balance of minerals in your blood. The imbalance may cause you to have a heat emergency.

Most individuals with cystic fibrosis die young as there is no cure for CF. Many people affected die in their 20s and 30s from lung failure. However, with the continuous introduction of many new treatments, the life expectancy of a person with cystic fibrosis is increasing to ages as high as 40 or 50. Lung transplantation is often necessary as CF worsens. 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 which is important in creating sweat, digestive juices, and mucus. Although most people without CF 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.