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Defining Cystic Fibrosis

Cystic fibrosis (CF) is a genetic disorder that particularly affects the lungs and digestive system. More than 30,000 kids and young adults in the United States (70,000 worldwide) are affected by CF.

What is cystic fibrosis?

Cystic fibrosis affects the secretory glands, which make mucus and sweat because it disrupts the normal function of epithelial cells – cells that make up the sweat glands in the skin and that also line passageways inside the lungs, liver, pancreas, and digestive and reproductive systems.

The inherited CF gene directs the body's epithelial cells to produce a defective form of a protein called CFTR (or cystic fibrosis transmembrane conductance regulator) found in cells that line the lungs, digestive tract, sweat glands, and genitourinary system.

When the CFTR protein is defective, epithelial cells can't regulate the way that chloride (part of the salt called sodium chloride) passes across cell membranes. This disrupts the essential balance of salt and water needed to maintain a normal thin coating of fluid and mucus inside the lungs, pancreas, and passageways in other organs. The mucus becomes thick, sticky, and hard to move.

Thickened secretions can clog the lungs, causing coughing and wheezing. It can also cause lung infections. Normally, mucus in the lungs traps germs, which are then cleared out of the lungs. But in CF, the thick, sticky mucus and the germs it has trapped remain in the lungs, which can become infected. Over time, multiple infections can cause permanent harm to the lungs.

The thick, sticky mucous can make it hard to breathe because it blocks the lungs and the airways that carry air to and from the lungs. It can also block tubes or ducts in other parts of your body, affecting the pancreas, liver, intestines, sinuses and sex organs as well. It can also cause a unique form of diabetes and bone loss.

In the pancreas, thick mucus blocks the channels that would normally carry important enzymes to the intestines to digest foods. When this happens, the body can't process or absorb nutrients properly, especially fats. Kids with CF have problems gaining weight, even with a normal diet and a good appetite. It may also cause the bowel to not work properly. This can result in large, greasy stools, gas or stomach pain. Because of this, a child may have trouble gaining weight and growing.

It's important to remember that every person with CF has different symptoms. Depending on the severity of your child's CF and the age of your child, CF can be mild or life-threatening. Fortunately, with the medicines and therapies available today, most kids grow up to into active adults who achieve their own goals, have families, and fulfill their dreams.

CF affects more than 30,000 kids and young adults in the United States (70,000 worldwide).

Who gets it?

Cystic fibrosis (CF)is a genetic disease. To be affected with CF, a person needs two copies of a CF gene. Each parent must be a carrier. If you're a carrier, you'll have no symptoms of CF. Without having a child with CF, or genetic testing, you would not know your carrier status.

CF affects both males and females and people from all racial, ethnic and socio-economic groups. However, the disease is most common among Caucasians of Northern European descent.

CF is also common among Latinos and American Indians. The disease is less common among African Americans and Asian Americans.

Of all ethnic groups, Caucasians have the highest inherited risk for CF, and Asian Americans have the lowest. In the United States today, about 1 of every 3,600 Caucasian children is born with CF. This compares with 1 of every 17,000 African Americans and only 1 of every 90,000 Asian Americans. Although the chances of inherited risk may vary, CF has been described in every geographic area of the world among every ethnic population.

What causes it?

Scientists don't know exactly why the CF gene evolved in humans, but they have some evidence to show that it helped to protect earlier generations from the bacteria that cause cholera, a severe intestinal infection.

What we do know is that a defect in the CFTR gene causes cystic fibrosis (CF). This gene makes a protein that controls the movement of salt and water in and out of your body's cells. In people who have CF, the gene makes a protein that doesn't work well. This causes thick, sticky mucus and very salty sweat.

Research suggests that the CFTR protein also affects the body in other ways. This may help explain other symptoms and complications of CF.

More than a thousand known defects can affect the CFTR gene. The type of defect you or your child has may affect the severity of CF. Other genes also may play a role in the severity of the disease.

How is cystic fibrosis inherited?

Every person inherits two CFTR genes—one from each parent. Children who inherit a faulty CFTR gene from each parent will have CF.

Children who inherit one faulty CFTR gene and one normal CFTR gene are "CF carriers." CF carriers usually have no symptoms of CF and live normal lives. However, they can pass the faulty CFTR gene to their children.

The image below shows how two parents who are both CF carriers can pass the faulty CFTR gene to their children.

Example of an inheritance pattern for cystic fibrosis


The image shows how CFTR genes are inherited. A person inherits two copies of the CFTR gene—one from each parent. If each parent has a normal CFTR gene and a faulty CFTR gene, each child has a 25 percent chance of inheriting two normal genes; a 50 percent chance of inheriting one normal gene and one faulty gene; and a 25 percent chance of inheriting two faulty genes.

Signs and symptoms

The signs and symptoms of cystic fibrosis (CF) vary from person to person and over time. Sometimes you'll have few symptoms. Other times, your symptoms may become more severe.

One of the first signs of CF that parents may notice is that their baby's skin tastes salty when kissed, or the baby doesn't pass stool when first born.

Most of the other signs and symptoms of CF happen later. They're related to how CF affects the respiratory, digestive, or reproductive systems of the body.

Respiratory system signs and symptoms

People who have CF have thick, sticky mucus that builds up in their airways. This buildup of mucus makes it easier for bacteria to grow and cause infections. Infections can block the airways and cause frequent coughing that brings up thick sputum (spit) or mucus that's sometimes bloody.

People who have CF tend to have lung infections caused by unusual germs that don't respond to standard antibiotics. For example, lung infections caused by bacteria called mucoid Pseudomonas are much more common in people who have CF than in those who don't. An infection caused by these bacteria may be a sign of CF.

People who have CF have frequent bouts of sinusitis (si-nu-SI-tis), an infection of the sinuses. The sinuses are hollow air spaces around the eyes, nose, and forehead. Frequent bouts of bronchitis (bron-KI-tis) and pneumonia (nu-MO-ne-ah) also can occur. These infections can cause long-term lung damage.

As CF gets worse, you may have more serious problems, such as pneumothorax (noo-mo-THOR-aks) or bronchiectasis (brong-ke-EK-ta-sis).

Some people who have CF also develop nasal polyps (growths in the nose) that may require surgery.

Digestive system signs and symptoms

In CF, mucus can block tubes, or ducts, in your pancreas (an organ in your abdomen). These blockages prevent enzymes from reaching your intestines.

As a result, your intestines can't fully absorb fats and proteins. This can cause ongoing diarrhea or bulky, foul-smelling, greasy stools. Intestinal blockages also may occur, especially in newborns. Too much gas or severe constipation in the intestines may cause stomach pain and discomfort.

A hallmark of CF in children is poor weight gain and growth. These children are unable to get enough nutrients from their food because of the lack of enzymes to help absorb fats and proteins.

As CF gets worse, other problems may occur, such as:

  • Pancreatitis (PAN-kre-ah-TI-tis). This is a condition in which the pancreas become inflamed, which causes pain.
  • Rectal prolapse. Frequent coughing or problems passing stools may cause rectal tissue from inside you to move out of your rectum.
  • Liver disease due to inflamed or blocked bile ducts.
  • Diabetes
  • Gallstones

Reproductive system signs and symptoms

Men who have CF are usually infertile because they're born without a vas deferens. The vas deferens is a tube that delivers sperm from the testes to the penis.

Women who have CF may have a hard time getting pregnant because of mucus blocking the cervix or other CF complications.

Other signs, symptoms, and complications

Other signs and symptoms of CF are related to an upset of the balance of minerals in your blood.

CF causes your sweat to become very salty. As a result, your body loses large amounts of salt when you sweat. This can cause dehydration (a lack of fluid in your body), increased heart rate, fatigue (tiredness), weakness, decreased blood pressure, heat stroke, and, rarely, death.

CF also can cause clubbing and low bone density. Clubbing is the widening and rounding of the tips of your fingers and toes. This sign develops late in CF because your lungs aren't moving enough oxygen into your bloodstream.

Low bone density also tends to occur late in CF. It can lead to bone-thinning disorders called osteoporosis and osteopenia.

In the past, doctors diagnosed most kids with CF by the time they were 3 years old, after growth problems or lung disease were present. Now, CF testing is part of the newborn screen in all 50 states. This screen may diagnose infants before symptoms begin.

Other symptoms include:

  • Meconiumileus in the newborn (intestinal blockage)
  • Frequent lung infections or pneumonia
  • Persistent wheezing
  • Persistent cough with thick mucus
  • Bulky, light-colored, foul-smelling bowel movements or diarrhea (because food isn't being digested properly)
  • Failure to gain weight, even though the child eats normal amounts
  • Very salty sweat
  • Poor height growth
  • Nasal polyps (small growths of tissue inside the nose)
  • Frequent sinus infections
  • Fatigue

People with CF get frequent lung infections that can damage their lungs over time and require strong antibiotics along with stays in the hospital. They may have trouble growing or gaining weight because of digestive problems.

Teens and adults with CF may also develop other illnesses, such as diabetes (when blood sugar is too high) or osteoporosis (a weakening of the bones).

We're here to help.

If you've been told your child might have CF, we know you've lots of questions. We can help. To schedule an appointment, refer a patient or speak to our staff, please call our offices at 682-885-6299. After hours and on weekends/holidays, call 682-885-4000 and ask the operator to page the pulmonologist on call.