Cystic fibrosis is a disease that causes the body to produce thick, sticky mucus. As the mucus builds up in the lungs, it blocks the airways and promotes the growth of bacteria. As a result, patients experience chronic lung infections that cause increasing damage to the lungs.

The mucus also may block ducts in the pancreas, which prevents digestive enzymes from reaching the small intestine. Without these enzymes, the body cannot fully absorb fats and proteins. This can lead to malnourishment and other symptoms. Cystic fibrosis also may create mineral imbalances, affect the liver and result in infertility.

A defect in the gene known as cystic fibrosis transmembrane conductance regulator (CFTR) causes cystic fibrosis. Everyone inherits one copy of the CFTR gene from each parent. When both parents pass on an abnormal CFTR gene, the child will have cystic fibrosis.

Symptoms of cystic fibrosis vary from patient to patient. Many patients with mild forms of this illness do not experience symptoms until they reach adolescence or young adulthood. Once symptoms appear, they are usually related to the thick, sticky mucus that is characteristic of the disease. Even if the symptoms are initially mild, they usually get steadily worse over time.

Most children who have cystic fibrosis are diagnosed by the time they are 3 years old, although milder forms of the illness may not be diagnosed until the teen years. Various tests are performed to diagnose the disease, including a sweat test that looks for abnormally high concentrations of salt in perspiration.

There is no known cure for cystic fibrosis. Treatments focus on improving the patient's capacity to breathe and eliminating infections. Chest physical therapy (CPT) is commonly used to loosen mucus. In this therapy, patients are gently but firmly pounded on the chest and back to dislodge mucus from the lungs. Medications also may help alleviate infections and other symptoms.

Although patients cannot prevent cystic fibrosis, they can take several steps that may reduce symptoms or make them more manageable. Patients are encouraged to lead a healthy lifestyle, including eating a well-balanced diet, exercising regularly and avoiding smoking.

Decades ago people with cystic fibrosis never survived to adulthood, but medical advances have increased the average life span to more than 35 years, according to the National Institutes of Health (NIH).