Abstract The availability of the human genome sequence and tools for interrogating individual genomes provide an unprecedented opportunity to apply genetics to medicine. Mendelian conditions, which are caused by dysfunction of a single gene, offer powerful examples that illustrate how genetics can provide insights into disease. Cystic fibrosis, one of the more common lethalautosomal recessive Mendelian disorders, is presented here as an example. Recent progress in elucidating disease mechanism and causes of phenotypic variation, as well as in the development of treatments, demonstrates that genetics continues to play an important part in cystic fibrosis research 25 years after the d iscove1y of the disease-causing gene.
Cystic fibrosis CF is an inherited disease caused by a defective gene, which affects tissues that produce mucus secretions. Affected organs typically include the lungs, the gastrointestinal tract, the pancreas and the liver.
Cystic fibrosis can also affect the sweat glands and the male reproductive system. The specific defective gene in cystic fibrosis controls production of 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 the affected organs.
The thickened mucous causes respiratory and digestive problems. A person with CF is prone to pneumonia and other lung infections, because the thickened secretions are more difficult to clear out of the breathing passages. Thick mucus in the pancreas interferes with the ability to properly digest foods.
In particular, several pancreatic enzymes needed to adequately break down and absorb fats are absent. This prevents absorption of nutrients from the intestinal tract and causes malnutrition. Incidence and Prevalence Cystic fibrosis is an autosomal recessive genetic disorder. In order to inherit the disease, a child must have inherited the defective gene from both parents.
A person can carry the defective gene, but not show symptoms of the disease. This person is known as a "carrier" of the disorder. Many people are carriers of the CF gene. In the general U. If both parents are carriers, any child will have a 1 in 4 chance of developing the disease. Cystic fibrosis is more common among whites of Northern Central European descent.
It is much less common in other ethnic groups. Approximately 30, Americans have CF, and 1, new cases are diagnosed each year. Cystic fibrosis is usually diagnosed before age 3, but sometimes it is diagnosed later. Symptoms The gene responsible for CF was identified by researchers in We now realize that there are more than different defective cystic fibrosis genes, causing vast variation in the severity of the disease.
In the 20 percent of cases that present in the newborn period, there might be a condition called "meconium ileus", in which passage of the first stool is delayed more than 48 hours. In an older child, the first sign of CF might be: About 50 percent of children with cystic fibrosis first see the doctor for respiratory complaints, such as pneumonia, sinusitis, frequent coughing or wheezing.
Once a diagnosis of cystic fibrosis is established, patients and parents should prepare for the following symptoms: Pneumothorax collapsed lungliver disease, diabetes, osteoporosis and osteomalacia may all result secondary to cystic fibrosis.
Treatment Treatment for cystic fibrosis is aimed at improving quality of life and extending survival. This can be best accomplished by early diagnosis and treatment from a comprehensive, multidisciplinary treatment program.
Specialty treatment programs for cystic fibrosis are available in many communities. Major components of treatment include medication and postural drainage with chest percussion.
Medications include antibiotic therapy for respiratory infections and pancreatic enzymes to replace those that are missing hence aiding digestion.
Vitamin supplements can be used to correct the malabsorption. Postural drainage with chest percussion helps break up the thick secretions in the lungs.Cystic fibrosis is a common genetic disease within the white population in the United States.
The disease occurs in 1 in 2, to 3, white newborns. Cystic fibrosis is less common in other ethnic groups, affecting about 1 in 17, African Americans and 1 in 31, Asian Americans.
Cystic Fibrosis Genetic Testing The Tag-It™ Cystic Fibrosis Kit is the first FDA-approved DNA-based blood test that helps detect cystic fibrosis. Genetic testing detects a limited number of the 1, genetic variations in the CFTR gene.
INTRODUCTION. Cystic fibrosis (CF) is a multisystem disease affecting the lungs, digestive system, sweat glands, and the reproductive tract. Patients with CF have abnormal transport of chloride and sodium across secretory epithelia, resulting in thickened, viscous secretions in the bronchi, biliary tract, pancreas, intestines, and reproductive system .
The Genetics of Cystic Fibrosis. Cystic fibrosis (CF) is a genetic disease. This means that CF is inherited. A child will be born with CF only if two CF genes are inherited- .
Cystic fibrosis (OMIM ) is a life-limiting autosomal recessive disorder that affects 70, individuals worldwide. The condition affects primarily those of European descent, although cystic fibrosis has been reported in all races and ethnicities. Cystic fibrosis is a disease whose most important symptom is the secretion of large amounts of mucus into the lungs, resulting in death from a combination of effects but usually precipitated by upper respiratory infection.