Cystic fibrosis shows a range of forms from mild to severe. Characteristically, CF individuals produce unusually salty sweat. The epithelial cells lining their internal organs produce excessive sticky mucus. The pancreas is affected; it does not produce enough enzymes to digest proteins. But, it is in the airways of the lungs that the major problem lies: here the mucus harbours persistent and recurrent infections. Despite daily physiotherapy and treatment with drugs, many people with CF eventually succumb to lung infections and die. At present the average age of death is about thirty, but the situation is improving and life expectancy continues to rise.
Another hallmark of the disease is infertility in men. This is becoming an increasingly significant factor as more CF sufferers reach adulthood.