Cystic Fibrosis, part 1 — Introduction, incidence, symptoms and treatment
What is cystic fibrosis?
Cystic fibrosis (CF) is an inherited disease, caused by a defective gene,
that affects tissues that produce mucus secretions. These include the
tissues that line the airways in the lungs, the gastrointestinal tract,
the ducts of the pancreas, and the ducts of the liver. Cystic fibrosis
can also affect the sweat glands and the male reproductive system.
The
defective gene is the one responsible for making cystic fibrosis transmembrane
conductance regulator (CFTR). CFTR is a protein that controls the flow
of chloride ions into and out of particular cells. In a person with CF,
malfunctioning or absent CFTR prohibits chloride from entering or leaving
cells, resulting in the production of thick, sticky mucus that clogs ducts
or tubes in lungs, pancreas and other parts of the body.
This results in respiratory and digestive problems. CF affects both the
mucus and sweat glands of the body.
A person with CF is prone to pneumonia and other lung
infections, due to thick mucus secretions in the breathing passages. Similarly, mucus
in the pancreas interferes with the process of digestion. Several pancreatic
enzymes involved in the breakdown and absorption of fats are absent. This
results in inadequate absorption of nutrients from
the intestinal tract and, thus, malnutrition.
Incidence and Prevalence
Cystic fibrosis is an autosomal recessive genetic disorder. This means
that, in order to inherit the disease, a child must have two parents who
carry the defective gene. If both parents are carriers of the defective
gene, there is a one in four chance that the baby will have cystic fibrosis.
Many people are carriers of a single CF gene. In the general population,
approximately 1 in 31, or 2-5% of the population of Americans, is a carrier
of the CF gene.
Cystic fibrosis is more common in Caucasians of Northern
Central European descent. It is much less common in other ethnic groups.
Approximately one in 2500 Caucasians has cystic fibrosis. About 1,000
new cases are diagnosed each year and about 30,000 American children and
young adults have CF. A diagnosis of cystic fibrosis is usually made before
the child’s third birthday, but it may be diagnosed later.
Symptoms
The gene responsible for CF was identified by researchers in 1989. That
discovery has led to the knowledge that there are more than 200 different
defects in the cystic fibrosis gene, which may result in varying degrees
of severity of the disease.
Cystic fibrosis may be characterized by a variety of symptoms, dependent
on the disease severity. In newborns, meconium ileus or delay of more
than 48 hours before passing a stool, is evident in 20% of all cases.
In an older infant, the first sign of CF may be stools which are bulky,
greasy, pale or clay colored and have a foul odor; poor weight gain; flabby
muscle tone or slow growth. In infants, the skin may have a salty taste.
About 50% of children with cystic fibrosis first see the doctor for recurrent
respiratory infections, such as pneumonia or sinusitis, or frequent coughing
and/or wheezing.
Once a diagnosis of cystic fibrosis is made, patients of all ages experience
the following symptoms. Due to the digestive problems associated with
CF, persons with the disease may experience diarrhea, weight loss or delayed
growth. Dehydration is common, due to the loss of so much sodium in the
sweat. In addition, fatigue is a common symptom of cystic fibrosis. CF
causes impaired reproductive function. Approximately 98% of adult males
produce little or no sperm, and females experience both decreased fertility
and more frequent complications during pregnancy and childbirth. One of
the most significant symptoms of cystic fibrosis is infections, particularly
in the lungs. These chronic infections destroy lung tissue, a complication
that ultimately takes the lives of most people with cystic fibrosis.
Cystic fibrosis may result in other complications or concurrent diagnoses.
Pneumothorax (collapsed lung), liver disease, diabetes mellitus, osteporosis
and/or osteomalacia may result from cystic fibrosis.
Treatment
Treatment for cystic fibrosis is aimed at improving quality of life and
lengthening survival time. This can best be accomplished by early diagnosis
and treatment from a comprehensive, multidisciplinary treatment program.
Specialty treatment programs for cystic fibrosis can be found in many communities.
Major components of treatment include medication and postural drainage,
or chest percussion.
Medications include antibiotic therapy for respiratory
infections and pancreatic enzymes to replace those that are missing and
aid in digestion. Vitamin supplements are often prescribed due to
the problems associated with malabsorption.
Postural drainage, or chest percussion, is intended
to help break up the thick secretions in the lungs. Traditionally, this
has been done by manual “clapping” over the child’s
chest and back. More recently, vests have been designed that, when worn
and turned on, vibrate to aid in loosening secretions in the lungs. Inhaled
bronchodilators and other breathing treatments are used to relieve chronic
obstruction of airways.
Lung transplantation has been utilized for some patients with cystic
fibrosis. This procedure does not “cure” the disease, but
allows the patient to have lungs that have not suffered from years of
insult due to CF. In other words, the procedure may increase survival
time, as the new lungs are not damaged by the disease process.
New treatments
also include replacement of the DNAse enzyme. A medication, called domase
(Pulmozyme), is now available. Research in the field of genetics is exploring
the possibility of correcting the disease by artificially inserting a
“normal” gene into the person with the defective CFTR gene.
This treatment, called gene therapy, and another form of intranasal gene
therapy, is currently undergoing clinical trials. Further promising research
is focusing on methods to correct the disorder before birth.
Possible medication side effects
The medications taken for cystic fibrosis have minimal side effects.
There are no side effects from the pancreatic enzymes that are part of
the treatment for CF. Some antibiotics may have side effects such as stomach
cramping, nausea and diarrhea. If the CF patient is taking bronchodialators,
some of those may cause nervousness or hyperactivity. At times, a child
with cystic fibrosis may be prescribed steroids to reduce inflammation.
Steroids can cause mood swings, ranging from anger to tearfulness.
Physical, dietary and other restrictions
The person with cystic fibrosis has no particular dietary restrictions,
unless he/she has developed diabetes mellitus. In that case, the child
will need to ascribe to a diabetic diet and may need to take insulin.
If diabetes mellitus is not an issue, the child may eat whatever he/she
wants and should have high calorie, protein, and nutrient consumption.
High-fat diets are encouraged for children with CF. Parents, physicians
or nurses are good contact persons to determine any special dietary needs
or restrictions for the child.
CF, Part 1 — Introduction, incidence, symptoms and treatment
For more information, please contact:
Kathy Davis, MSEd, PhD
kdavis2@kumc.edu
(913) 588-6305