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Symptoms of Cystic Fibrosis


Updated May 27, 2014

Cystic fibrosis (CF) is a chronic, progressive disease and symptoms increase as the disease progresses.

First Symptom

Most of the time newborns with cystic fibrosis look just like healthy babies because the disease does not cause any visible abnormalities in the early stages. About 20% of the time, babies with CF will have a serious intestinal obstruction at birth called a meconium ileus. This type of obstruction rarely occurs unless a baby has CF, so if it occurs it is usually considered the first symptom.

Early Symptoms

If cystic fibrosis is not detected at birth, other symptoms will usually begin to appear in the first year or two of life.

Poor Weight Gain
Blockages in the pancreas and intestinal glands prevent the digestive system from working properly. Foods that are eaten pass through the body without many nutrients being absorbed, resulting in poor growth. If a baby has not regained his or her birth weight by 4-6 weeks of age or shows an ongoing pattern of poor growth, the doctor may begin to suspect CF.

Huge Appetite
Because the nutrients are not absorbed from foods, the brain tries to meet the body’s energy requirement by sending hunger signals. People with cystic fibrosis will often have voracious appetites and can consume tremendous amounts of food without resulting weight gain.

Bulky, Oily, Foul Smelling Bowel Movements
The poorly functioning digestive system has particular trouble digesting fats and proteins. Much of what would normally be absorbed by a healthy digestive system is excreted by the bowels, resulting in the abnormal bowel movements that often occur in patients with CF.

Frequent Cough and Respiratory Infections
Coughing, difficulty breathing, and frequent respiratory infections are often the first symptoms recognized by parents of children with CF.

These symptoms occur because:







  • Thick mucus builds up in the lungs and clogs air passages, interfering with breathing.
  • The brain recognizes the problem and tries to correct it by sending a message to the lungs to cough.
  • The coughing is ineffective because the mucus is too thick and sticky for the lungs to be able to clear.
  • Airways become swollen and irritated from the stress of coughing and trying to breathe.
  • This narrows the air passageways even further and causes more thick mucus to become trapped.
  • Trapped mucus is a breeding ground for bacteria, leading to frequent respiratory infections.


Salty Skin
The genetic defect that causes cystic fibrosis interferes with the body’s ability to move salt in and out of cells. The salt that cannot be absorbed is excreted through the skin by the sweat glands, resulting in the telltale sign of salty tasting sweat. Sometimes, there may even be visible salt deposits on the skin. Salt excretion by the sweat glands is the basis of the most common test used to diagnose cystic fibrosis.

Advanced Symptoms and Complications

Advanced symptoms of cystic fibrosis are not usually symptoms of the disease itself, but symptoms of the damage that CF causes over time. By the time these conditions appear, most people already know that they have cystic fibrosis and have been living with the disease for quite some time.

Delayed Puberty
Delayed puberty is sometimes seen in girls with cystic fibrosis as a result of poor nutrition.

Most males with cystic fibrosis are infertile because of secretions blocking the passage of sperm. Women may experience infertility as a result of thick cervical mucus blocking the entry of sperm into the reproductive organs.

Over time, the damage done to the pancreas by cystic fibrosis causes it to stop producing enough insulin. About 15% of the people with cystic fibrosis that reach adulthood will develop insulin dependent diabetes.

Liver Disease
Blockage of bile ducts in the liver causes scarring and liver damage in about 5% of cystic fibrosis patients. If liver damage does occur, it is usually seen in adults.

Gallbladder Disease
The gallbladder stores a substance called bile that is created by the liver and aids in the digestion of fat. In many people with cystic fibrosis, the bile is thick and cannot pass through the bile duct to leave the gallbladder. Most of the time this does not produce symptoms, but about 10% of cystic fibrosis will develop gallstones requiring surgery.


When bile leaves the gallbladder, it travels into the small intestine through the common bile duct that is shared with the pancreas. If a gallstone leaves the gallbladder and gets stuck in the common bile duct, pancreatic secretions can’t get through. This causes a very painful swelling and irritation of the pancreas known as pancreatitis, which requires surgical intervention.


The Merck Manual. Cystic Fibrosis. February 2003.

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