Cystic Fibrosis (CF) is a chronic progressive disease caused by an inherited genetic defect. It affects all mucus secreting tissues, but particularly the respiratory and digestive tracts. 

The most common fatal genetic disease in Caucasians, 90% percent of CF deaths are due to pulmonary (lung) infections. CF is not contagious and therefore you cannot "catch" it from someone. In the past it was considered a child's disease since few survived to the age of 30. Due to medical advances within the past decade, people with CF now have an average life expectancy of 30 years. Dramatic strides in genetic and biomedical research hold forth the promise of further treatment improvements.

OCCURRENCE

One in twenty people carry the CF gene but exhibit no symptoms of the disease. That amounts to 12 million carriers in the United States with many unaware they harbor a defective gene.  CF occurs when an individual inherits two abnormal genes, one from each parent. When both parents are carriers of a abnormal gene each of their children has a 25% chance of being born with CF, a 50% chance of being an asymptomatic carrier, and a 25% chance of being normal (not a carrier). Roughly one in every 3000 babies is born with CF and approximately 30,000 Americans suffer from the disease. The majority of those living with CF are children.

CAUSES

Every gene in our DNA has two copies.  One of these genes, on chromosome number 7, causes the body to produce  a special protein called CFTR (Cystic Fibrosis Transmembrane Regulator). CFTR regulates the flow of chloride ions across cell membranes. It is located in cells lining the passageways of the lungs, pancreas, colon, and genitourinary tract. If one of the  gene's copies is normal, the body produces normal levels of CFTR. An individual with two CF alleles has abnormal CFTR production, which interferes with the cell membrane chloride flow. This individual has cystic fibrosis.

CF ACTIONS ON THE BODY

Cystic fibrosis affects all mucus secreting tissues. CF patients' thick and dehydrated mucus accumulates in the intestines and lungs. This thick mucus results in chronic respiratory infections, the growth of nasal polyps (fleshy growths inside the nose) and blocking of the pancreatic ducts. The pancreatic ducts carry digestive enzymes from the pancreas to the intestines and without sufficient enzymes food is not completely digested and exits through the bowel. People with CF also lose large amounts of salt when they sweat. This upsets the balance of minerals in the blood, which may lead to abnormal heart rhythms. The results of these abnormal body functions are malnutrition, poor growth, chronic respiratory infections and permanent lung damage. Lung disease causes the death of most patients.

SYMPTOMS

Cystic fibrosis symptoms may manifest at birth or not be diagnosed until years later in the teens or even early adulthood. Symptom severity varies from one individual to the next. The reasons for individual variations are not understood, but believed to be a combination of genetic and environmental factors.

Common CF symptoms include: 

• Salty tasting skin    

• Persistent cough or recurrent pneumonia

• Excessive appetite, but difficulty gaining weight

• Large strong smelling, greasy stools

DIAGNOSIS

The Sweat Test: In a 1953 New York City heat wave physicians noticed children with cystic fibrosis losing massive amounts of salt in their sweat. These observations resulted in the development of the sweat test for the presence of cystic fibrosis, which is still used today. The sweat test measures the concentration of salt (sodium chloride) in sweat. The procedure consists of forcing  an area of skin (usually on the arm) to sweat by using the chemical pilocarpine and a mild electric current. Sweat test results showing higher than normal sodium and chloride levels indicate that the person has cystic fibrosis. A small percentage of people with CF have normal sweat chloride levels and the test is inaccurate in newborns because they do not produce enough sweat. In these cases, other types of tests are used.

• The Immunoreactive Trypsinogen Test (IRT): The IRT analyzes a blood sample 2 to 3 days after birth for a protein called trypsinogen. Positive IRT tests must be confirmed by other tests.

• Chest x-rays and Lung Function Tests

• Sputum (phlegm) Cultures

• Stool Sample Analysis to identify typical CF digestive abnormalities.

• Genetic Testing: Since the discovery of the CF gene accurate tests for identifying its presence have been developed.

TREATMENT

Currently there is no cure for Cystic Fibrosis, but future treatment possibilities include advances in drugs and gene therapy. Drugs under research include those that  guide mutant CFTR molecules through the cell membrane and gene therapy which would deliver normal CFTR genes to abnormal ones.

CONVENTIONAL TREATMENT

Conventional methods treat the symptoms, not the disease but are important in maintenance of CF.

• Chest physiotherapy (CPT): Chest physiotherapy consists of bronchial, or postural, drainage, performed by placing the person with CF in a position that allows mucus to drain from the lungs. The chest or back is then clapped (percussed) to dislodge the mucus. This procedure is done over different parts of the back and chest to loosen the mucus throughout the lungs. Mechanical aids are available for performing the therapy.

• Exercise:  Exercise helps loosen mucus and also stimulates coughing to aid in its removal.

• Medications: Aerosolized and inhaled medications are used to improve breathing. These include decongestants to reduce respiratory swelling, mucolytics to help thin the mucus, and bronchodilators to enlarge the breathing tubes. Antibiotics fight lung infections and may be taken orally, in aerosol form, or by injection.

• Supplemental enzymes and a regulated diet: CF digestive problems are more easily managed than the respiratory problems. A diet low in fat, high in protein and high in calories is often used along with pancreatic enzymes supplements. The pancreatic enzymes are important for digestion and the ducts, which normally deliver them to the intestine, are often blocked by mucus in CF. Vitamin A, D, E, and K supplements are given to ensure good nutrition.

• Enemas and mucolytic agents: may be needed to treat intestinal obstructions.

Gene Therapy

Since the identification of the CF gene in 1989, many advances have occurred in the field of genetics. Impressive progress is being made in developing ways to treat the gene abnormality that causes CF. An animal research model  using mice with CF has produced great strides in understanding the mechanisms of  the disease. Based on this research scientists have been successful in growing cells from the nasal passages of CF patients. By inserting the normal gene into these cells, the researchers corrected the cells' membrane chloride transport abnormality. Normal copies of the defective gene can be produced and used to treat defective cells. Current research focuses on how to utilize this procedure within a patient’s body to treat a large number of CF cells. These trials are occurring worldwide in animal CF models. This procedure is called gene delivery.  

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