Cystic Fibrosis is a disease which affects the body's exocrine glands, including the pancreas, sweat glands, and the lungs. It is a hereditary disease most common in white children, occuring in about one in every 2000 births. It is less common among African-American children. (about one in 17,000 births), and even more rare among Orientals (one in 100,000 births ) The mode of inheritance is autosomal which means that it does not involve the x or y chromosomes, which determine sex. It is also recessive, which means that the disease is inherited from both parents. About five percent caucasian Americans are believed to carry the gene.
The number of CF carriers is likely to increase in the future. Formerly CF patients rarely lived to adulthood, but improvements in treatment allow many to survive into their thirties or forties and have children of their own. The disease varies considerably in severity. Some cases are vary mild, and may not be diagnosed until adulthood.
The probabilities of producing offspring who either have the disease or are carriers of the genetic defect are listed in figure 1.
Figure 1. Probability of Having a Child With Cystic Fibrosis
Parents Chance of
Unaffected ChildChance of
Child CarrierChance of
Child with CFUnaffected + Carrier 50% 50% 0 Two Carriers 25% 50% 25% Unaffected + CF Patient 0 100% 0 Carrier + CF Patient 0 50% 50%
Signs and Symptoms
The signs and symptoms of CF vary, depending on how severe the disease is and the degree of bacterial infection. Almost always, a productive cough is present, and very often patients appear barrel-chested. Frequent hospitalizations are a result of recurring respiratory, gastrointestinal, and nutritional problems.
CF is characterized by the production of very thick and sticky mucus. The ducts leading from the pancreas become obstructed, preventing normal digestion of food. This leads to poor absorption of the nutrients in the food, and ultimately to malnutrition. About 90 percent of CF cases involve the lungs. Lung infections are common among children with CF and may lead to extreme weakness. Severe cases of CF ultimately may lead to heart disease.
Treatment
Over the past 25 years, treatment for CF has improved dramatically. Much of the care has centered on improved breathing through the use of inhaled bronchodilators. New and more effective antibiotics have been better able to manage the chronic infections. During severe infections which might require hositalization, inhaled antibiotics are sometimes used. In a few cases, single and double lung or heart-and-lung transplants have been tried successfully.
A Possible Cure?
In 1985, the specific gene that causes CF, was identified. That same year, a screening test for newborns was introduced. Laboratory tests of gene therapy have been successful. Small group tests of a genetically engineered enzyme have also been successful. The enzyme, administered in aerosol form, thins out the mucus in the patient's lungs, making it easier to clear by coughing. Testing on this treatment continues. It's now FDA approved. Life expectancy for CF patients continues to increase. With all of the investigations underway in gene therapy, improved drugs, and transplant experience, the future of CF patients appears brighter than ever before.
Reviewed: August, 2002.