The sweat glands and the reproductive system usually are involved, as well. A person with CF makes too much thick, sticky mucus. This clogs the air passages in the lungs. It makes the person more likely to get an infection. The clogged passages also make it harder to breathe. The sweat of a person with CF often is saltier than normal. Thick secretions also clog the ducts of the pancreas. This keeps digestive enzymes and other chemicals made by the pancreas from helping with digestion. Most men with CF are infertile. Most women with CF have difficulty getting pregnant.

Symptoms can vary from child to child. More than 8 in 10 people with CF are diagnosed by age 2. Some children with CF may not be diagnosed until they are teens.

An abnormality in the glands that make mucus causes the mucus to be thick. The mucus builds up in the intestines and lungs. This causes malnutrition, poor growth, and breathing problems. The extra mucus becomes a place for bacteria to grow. This causes frequent respiratory infections. People with CF also lose too much salt when they sweat. A severe loss of salt can upset the heart's rhythm and may cause shock.

The pancreas helps in digestion by making enzymes and bicarbonate to neutralize stomach acid. If the pancreas ducts are blocked by mucus, digestion is affected. Bowel movements become bulky and foul-smelling. Malnutrition and slowed growth and development can also occur. If the cells in the pancreas that make insulin are damaged, the person can develop type 1 diabetes. If the bile ducts in the liver are affected, biliary cirrhosis may result. Other symptoms and problems linked with CF include sinusitis, nasal polyps, clubbing of fingers and toes, rupture of lung tissue, abdominal pain, gassiness, gallstones, coughing blood, enlargement of the right side of the heart, and infertility.

All newborns are screened for cystic fibrosis. The method of screening may vary from state to state. The sweat test measures the amount of salt (sodium chloride) in a person's sweat. A person with higher than normal amounts of sodium and chloride may have CF. A blood test called an immunoreactive trypsinogen test measures the level of a protein called trypsinogen. Higher levels of this protein may mean CF. Testing for CF also can be done during pregnancy to find out whether the developing fetus has the disease. Genetic testing also can be done to help figure out the diagnosis and for couples with a family history of CF who are considering having children.

The first medicines just for CF were released in 2012. They are called cystic fibrosis transmembrane conductance regulator (CFTR) modulators. These are the first treatment that targets the actual source of the disease, not just the symptoms. Other medicines focus on the symptoms of the disease. Bronchodilators widen the bronchial passages in the lungs. Antibiotics kill the bacteria that cause lung infections. Decongestants ease the swelling of bronchial membranes. Mucolytics thin the mucus in the lungs. Vitamin supplements and enzymes are also often given.

Fatty acids are long molecules that serve as the building blocks of the cell membrane. Certain fatty acids play a key role in controlling the body's inflammatory response. The hallmark of CF is chronic inflammation of the lung tissue. People with CF appear to have high levels of the fatty acid arachidonic acid (AA) and low levels of the fatty acid docosahexaenoic acid (DHA). This combination leads to tissue inflammation.

To have CF, a person must inherit 2 defective CF genes, 1 from each parent who carries the abnormal CF gene. Each time 2 carriers conceive, they have a 1 in 4 chance that their child will have CF. They also have a 1 in 2 chance that the child will be a carrier of the CF gene. And they have a 1 in 4 chance that the child will not be a carrier.