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Cystic Fibrosis

Cystic Fibrosis Overview

What is cystic fibrosis?

Cystic fibrosis or CF is an inherited disease involving epithelial cells. Epithelial cells are found lining the skin, sweat glands, and respiratory, gastrointestinal and genitourinary tracts. In people with cystic fibrosis, the epithelial cells do not function properly. These impaired cells cause abnormal regulation of the flow of salts and water. The result is abnormal secretions such as a thick, sticky mucus that clogs the lungs.

The abnormal secretions lead to various defects in the body. These include problems in the following areas:

Respiratory tract (lungs) - repeated lung and sinus infections (bronchitis, pneumonia, sinusitis).

Gastrointestinal tract (bowels) - impaired function of the pancreas occurs in 85% of CF cases. As a result, digestive enzymes may not reach the intestines to help break down food. Results can be meconium ileus at birth (a condition in which the initial newborn stool, called meconium, fails to pass and can result in intestinal obstruction). Later, there may be frequent loose stools, impaired uptake of fat, protein and certain vitamin nutrients, poor nutrition and/or poor weight gain. All of these abnormalities are related to failure of exocrine pancreatic function.

Sweat glands - excess salt lost in sweat may cause dehydration and metabolic imbalance.

Other - other organs affected include the liver, endocrine pancreas (related to diabetes), and reproductive systems (male, female).

 

What are the symptoms of cystic fibrosis?

Many different genes for CF exist; as a result, clinical characteristics and symptoms vary. Symptoms may range from mild to severe in different individuals with CF. The following symptoms generally represent classic or severe forms of the disease:

What causes cystic fibrosis?

The changes in epithelial cell function which cause the abnormal cellular secretions in CF are the result of an abnormal cell membrane protein called the cystic fibrosis transmembrane regulator (CFTR). The CFTR abnormality results from a defective gene on human chromosome 7. There are over 1000 known mutations within the CFTR gene, which can cause CF. The most common is the delta F 508 mutation, which accounts for about 70% of CF genes.

Roughly 1 in 30 Caucasians carry one copy of an abnormal CFTR gene. However, a person must have two copies of an abnormal CFTR gene to have CF. The disease is also seen, though much less frequently, in African American and Asian populations. This means a child will be born with CF only if the child receives one defective gene from each parent. After a child with CF is born, symptoms maybe be delayed for weeks, months or even years.

How does cystic fibrosis affect the body?

In normal airways, secretions work to help us remove germs and particles we breathe in with the outside air. In the airways of a person with CF, the secretions are abnormal and become thicker, actually trapping germs (mostly bacteria). This results in chronic infection. With time, infection leads to airway destruction and lung damage that progressively worsens.

Interestingly, the same cell abnormality in the pancreas, which is a digestive organ not in contact with outside air, leads to clogging of the ducts and destruction of the pancreas tissue itself. Because the damaged pancreas cannot release digestive juices, food in the intestinal tract is not broken down properly. Nutrients are then lost in the stool instead of being absorbed. The result is often diarrhea and poor nutrition.

How is cystic fibrosis diagnosed?

Cystic fibrosis may be diagnosed several different ways. A concerned physician or family member may request a sweat chloride test. This is usually done because:

During a sweat chloride test, a carefully-collected sample of sweat is analyzed for salt content. The test should be performed at an accredited CF center and results are usually available later the same day.

Alternatively, the diagnosis may occur because of:

Diagnosis may also occur because of specific genetic tests that show characteristic CF genes. These genetic tests are usually performed on a blood sample. Results take days to weeks.

In many cases, physicians who are experts in CF care may ask for both genetic tests and a sweat chloride test.

 

How is cystic fibrosis treated?

Treatment for each case of CF is somewhat individualized. The usual approach combines well child/adult care with a comprehensive home care program. This integrated approach is used to:

Periodic intensive medical management for reduction of pulmonary infection load is required. Physical activity and conditioning are also well recognized as an important part of in cystic health care maintenance. All treatments are monitored at accredited CF centers all over the country with the support of the Cystic Fibrosis Foundation.

 

What is the outlook for cystic fibrosis?

The future outlook for those with CF is optimistic. While cystic fibrosis is a life-shortening disease, the outlook is continually improving. Over the period from the 1950s and 1960s to the present, the median life expectancy has risen from 5-10 years to over 35 years, with some patients surviving into the fifth and sixth decades. In fact, some patients even survive into their seventies.

And even these figures probably underestimate current survival rates. This is because these figures reflect the impact of earlier and less effective treatment patterns used in older patients. With later and later years of birth, survival appears to improve progressively. Most CF patients become adults and should prepare for a full and productive life.

Much of this improved survival is attributed to hard work by families, intensive medical monitoring and care in CF centers, as well as increased options in antibiotics that can manage infection. Due to the intensive research efforts to defeat this disease, the expectation of added treatment options stemming from clinical trials at CF centers, and the refinement of lung transplantation for CF, continued progress is expected if combined with aggressive day-to-day therapy at home.

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Last Reviewed: Oct 15, 2008

Karen S McCoy, MD Karen S McCoy, MD
Professor of Pediatrics
Professor at the School of Allied Medical Professionals
College of Medicine
The Ohio State University