CF stands for Cystic Fibrosis. Cystic fibrosis (CF) is a life-threatening disease that causes mucus to build up and clog some of the organs in the body, particularly in the lungs and pancreas. When mucus clogs the lungs, it can make breathing very difficult. The thick mucus also causes bacteria (or germs) to get stuck in the airways, which causes inflammation (or swelling) and infections that leads to lung damage.
Mucus also can block the digestive tract and pancreas. The mucus stops digestive enzymes from getting to the intestines. The body needs these enzymes to break down food, which provides important nutrients to help us grow and stay healthy. People with cystic fibrosis often need to replace these enzymes with capsules they take with their meals and snacks to help digest the food and get the proper nutrition.
Cystic fibrosis is a genetic disease. That means people inherit it from their parents through genes (or DNA), which also determine a lot of other characteristics including height, hair color and eye color. Genes, found in the nucleus of all the body's cells, control cell function by serving as the blueprint for the production of proteins.
The defective gene that is responsible for causing cystic fibrosis is on chromosome 7. To have cystic fibrosis, a person must inherit two copies of the defective CF gene—one copy from each parent. If both parents are carriers of the CF gene (i.e., they each have one copy of the defective gene), their child will have a 25% chance of inheriting both defective copies and having cystic fibrosis, a 50% chance of inheriting one defective copy and being a carrier, and a 25% chance of not having CF or carrying the gene.
Approximately 30,000 people in the United States have cystic fibrosis. An additional ten million more—or about one in every 31 Americans—are carriers of the defective CF gene, but do not have the disease. The disease is most common in Caucasians, but it can affect all races.
The severity of cystic fibrosis symptoms is different from person to person. The most common symptoms are:
Very salty-tasting skin
A large appetite, but poor weight gain
Greasy, bulky bowel movements
Constant coughing, wheezing or shortness of breath
Many lung infections, like pneumonia and bronchitis
Small, fleshy growths in the nose called nasal polyps
Sometimes people are told that they have asthma or chronic bronchitis when they really have cystic fibrosis. New research shows that the severity of CF symptoms is partly based on the types of CF gene mutations (defects). Scientists have found more than 1,500 different mutations of the CF gene.
Most people are diagnosed with CF at birth or before the age of 3. A doctor who sees the symptoms will order either a sweat test or a genetic test to confirm the diagnosis.
A sweat test is the most common test used to diagnose cystic fibrosis. A small electrode is placed on the skin (usually on the arm) to stimulate the sweat glands. Sweat is then collected and the amount of chloride, a component of salt in the sweat, is measured. A high level of chloride—a score of more than 60 mmol/L (a measure of concentration)—means that the person has cystic fibrosis. Scores between 40 mmol/L and 60 mmol/L are considered to be on the borderline and need to be looked at on a case-by-case basis. Scores of less than 40 mmol/L are considered negative for CF. The best place to receive a reliable sweat test is at a Cystic Fibrosis Foundation-accredited care center.
In a genetic test, a blood sample or cells from the inside of the cheek is taken and sent to a laboratory to see if any of the various mutations of the CF gene are found. A genetic test is often used if the results from a sweat test are unclear.
Scientists have many different ideas about what goes wrong in the lungs of a person with cystic fibrosis, but it all begins with defective CF genes. Normally, the healthy CF gene makes a protein—known as CFTR (Cystic Fibrosis conductance Transmembrane Regulator)—that is found in the cells that line various organs, like the lungs and the pancreas. This protein controls the movement of electrically charged particles, like chloride and sodium (components of salt) in and out of these cells. When the protein is defective, as in cystic fibrosis, the salt balance in the body is disturbed. Because there is too little salt and water on the outside of the cells, the thin layer of mucus that helps keep the lungs free of germs becomes very thick and difficult to move. And because it is so hard to cough out, this mucus will clog the airways and lead to infections that damage lungs.