Cystic fibrosis.

Cystic fibrosis, an autosomal recessive disorder, is the most common genetic disease of Caucasians. One in 25 Caucasians are carriers of the gene. The gene is found far less commonly in other races. There are over 230 different alleles of the gene, located on the 7th chromosome. The gene encodes for a membrane protein that functions as an ion channel. The survival of cystic fibrosis patients has been gradually increasing, with a mean survival in 1990 of 28 years. If the current trend of improved survival continues, it is estimated that half of cystic fibrosis patients will be over 18 years old by 1996. Disease is found in many organs including the lungs, sinuses, pancreas, gastrointestinal tract, hepatobiliary system, sweat glands and reproductive tract. The majority of patients die of pulmonary disease. The airways become chronically colonized with bacteria that cannot be eradicated, leading to bronchitis, bronchiectasis, and finally, pulmonary fibrosis with respiratory failure. The pulmonary disease may be complicated by massive hemoptysis and pneumothorax. Patient survival rates have increased because of antibiotic therapy and improved nutrition with pancreatic enzyme replacements. New treatments for the pulmonary disease are under clinical trial and include antiproteases, amiloride, a sodium channel blocker, and DNase. The insertion of the normal cystic fibrosis allele into an animal model using a modified adenovirus with effective transcription suggests that gene therapy may be possible in the future, but safety and technical problems have to be addressed.