CYSTIC FIBROSIS DEFINITION
Cystic Fibrosis (CF) is an inherited disease that causes thickened mucus to form in the lungs, pancreas and other organs. In the lungs, this mucus blocks the airways, causing lung damage and making it hard to breathe. CF is a life-threatening condition, but thanks to advances in treatment and care, the average life expectancy has been steadily increasing and quality of life has improved.
CYSTIC FIBROSIS CAUSES
In cystic fibrosis, a defect (mutation) in a gene changes a protein that regulates the movement of salt in and out of cells. The result is thick, sticky mucus in the respiratory, digestive and reproductive systems, as well as increased salt in sweat.
Many different defects can occur in the gene. The type of gene mutation is associated with the severity of the condition.
Children need to inherit one copy of the gene from each parent in order to have the disease. If children inherit only one copy, they won’t develop cystic fibrosis, but will be carriers and possibly pass the gene to their own children.
CYSTIC FIBROSIS PATHOPHYSIOLOGY
Cystic fibrosis is caused by defects in the cystic fibrosis gene, which codes for a protein transmembrane conductance regulator (CFTR) that functions as a chloride channel and is regulated by cyclic adenosine monophosphate (cAMP). Mutations in the CFTR gene result in abnormalities of cAMP-regulated chloride transport across epithelial cells on mucosal surfaces.
Six classes of defects resulting from CFTR mutations have been described and are as follows :
- Complete absence of CFTR protein synthesis
- Defective protein maturation and early degradation (caused by the most common mutation, ΔF508)
- Disordered regulation (diminished ATP binding and hydrolysis)
- Defective chloride conductance or channel gating
- Diminished transcription due to promoter or splicing abnormality
- Accelerated channel turnover from the cell surface
CFTR mutations have poor penetrance. This means that the genotype does not predict the pattern or severity of disease.
Defective CFTR results in decreased secretion of chloride and increased reabsorption of sodium and water across epithelial cells. The resultant reduced height of epithelial lining fluid and decreased hydration of mucus results in mucus that is stickier to bacteria, which promotes infection and inflammation. Secretions in the respiratory tract, pancreas, GI tract, sweat glands, and other exocrine tissues have increased viscosity, which makes them difficult to clear.
Most patients with cystic fibrosis have severe chronic lung disease and exocrine pancreatic insufficiency. Additional manifestations include the following:
- Nasal polyposis
- Rectal prolapse
- Chronic diarrhea
- Cirrhosis or other forms of hepatic dysfunction
CYSTIC FIBROSIS SYMPTOMS
Screening of newborns for cystic fibrosis is now performed in all 50 states. As a result, the condition can be diagnosed within the first month of life, before symptoms develop. For people born before newborn screening was performed, it’s important to be aware of the signs and symptoms of cystic fibrosis.
Cystic fibrosis signs and symptoms vary, depending on the severity of the disease. Even in the same person, symptoms may worsen or improve as time passes. Some people may not experience symptoms until adolescence or adulthood.
People with cystic fibrosis have a higher than normal level of salt in their sweat. Parents often can taste the salt when they kiss their children. Most of the other signs and symptoms of cystic fibrosis affect the respiratory system or the digestive system. However, adults with cystic fibrosis are more likely to have atypical symptoms, such as pancreatitis, diabetes and infertility.
RESPIRATORY SIGNS AND SYMPTOMS
The thick and sticky mucus associated with cystic fibrosis clogs the tubes that carry air in and out of your lungs. This can cause:
- A persistent cough that produces thick (sputum) mucus
- Exercise intolerance
- Repeated lung infections
- Inflamed nasal passages or a stuffy nose
DIGESTIVE SIGNS AND SYMPTOMS
The thick mucus can also block tubes that carry digestive enzymes from your pancreas to your small intestine. Without these digestive enzymes, your intestines can’t fully absorb the nutrients in the food you eat. The result is often:
- Foul-smelling, greasy stools
- Poor weight gain and growth
- Intestinal blockage, particularly in newborns (meconium ileus)
- Severe constipation
Frequent straining while passing stool can cause part of the rectum — the end of the large intestine — to protrude outside the anus (rectal prolapse). When this occurs in children, it may be a sign of cystic fibrosis. Parents should consult a physician knowledgeable about cystic fibrosis. Rectal prolapse in children may require surgery.
CYSTIC FIBROSIS DIAGNOSIS
Doctors diagnose cystic fibrosis (CF) based on the results from various tests.
All States screen newborns for CF using a genetic test or a blood test. The genetic test shows whether a newborn has faulty CFTR genes. The blood test shows whether a newborn’s pancreas is working properly.
If a genetic test or blood test suggests CF, a doctor will confirm the diagnosis using a sweat test. This test is the most useful test for diagnosing CF. A sweat test measures the amount of salt in sweat.
For this test, the doctor triggers sweating on a small patch of skin on an arm or leg. He or she rubs the skin with a sweat-producing chemical and then uses an electrode to provide a mild electrical current. This may cause a tingling or warm feeling.
Sweat is collected on a pad or paper and then analyzed. The sweat test usually is done twice. High salt levels confirm a diagnosis of CF.
CYSTIC FIBROSIS TREATMENT
There is no cure for cystic fibrosis, but treatment can ease symptoms and reduce complications. Close monitoring and early, aggressive intervention is recommended. Managing cystic fibrosis is complex, so consider obtaining treatment at a center that specializes in cystic fibrosis.
The goals of treatment include:
- Preventing and controlling lung infections
- Loosening and removing mucus from the lungs
- Preventing and treating intestinal blockage
- Providing adequate nutrition
The options include:
- Antibiotics to treat and prevent lung infections
- Mucus-thinning drugs to help you cough up the mucus, which improves lung function
- Bronchodilators to help keep your airways open by relaxing the muscles around your bronchial tubes
- Oral pancreatic enzymes to help your digestive tract absorb nutrients
CHEST PHYSICAL THERAPY
Loosening the thick mucus in the lungs makes it easier to cough up. Chest physical therapy helps loosen mucus. It is usually done from one to four times a day. A common technique is clapping with cupped hands on the front and back of the chest.
Mechanical devices also can help loosen lung mucus. These include a vibrating vest or a tube or mask you breathe into.
Your doctor may recommend a long-term program to improve your lung function and overall well-being. Pulmonary rehabilitation is usually done on an outpatient basis and may include:
- Exercise training
- Nutritional counseling
- Breathing techniques
- Psychological counseling and group support
SURGICAL AND OTHER PROCEDURES
- Nasal polyp removal. Your doctor may recommend surgery to remove nasal polyps that obstruct breathing.
- Oxygen therapy. If your blood-oxygen level declines, your doctor may recommend you sometimes breathe pure oxygen to prevent high blood pressure in the lungs (pulmonary hypertension).
- Endoscopy and lavage. Mucus may be suctioned from obstructed airways through an endoscope.
- Feeding tube. Cystic fibrosis interferes with digestion, so you can’t absorb nutrients from food very well. Your doctor may suggest temporarily using a feeding tube to deliver extra nutrition while you sleep. This tube may be threaded through your nose to your stomach or surgically implanted into the abdomen.
- Bowel surgery. If a blockage develops in your bowel, you may need surgery to remove it. Intussusception, where a section of bowel has folded in on itself, also may require surgical repair.
- Lung transplant. If you have severe breathing problems, life-threatening lung complications or increasing resistance to antibiotics used to treat lung infections, lung transplantation may be an option. Because both lungs are affected by cystic fibrosis, both need to be replaced. CF does not recur in transplanted lungs.