Illustration of cystic fibrosis. It is characterised by thick, viscous mucus that prevents the digestive and respiratory tracts from functioning normally. The left-hand outline shows the organs affected by the illness: - The skin : abnormal sweat which is 3 to 5 times more salty. - The lungs : viscous mucus sticks to the bronchial tubes, making breathing difficult and increasing bronchial, viral and particularly bacterial infections. - The liver : affected in 15% to 20% of cases, thick bile blocks the biliary tracts preventing it from working properly. - The pancreas : affected in 80% of cases, mucus obstructs the pancreatic ducts preventing digestion enzymes from reaching the intestine. - The intestine : bad digestion causes abdominal pain and problems of digestive transit such as diarrhea or constipation. - The genital organs : male sterility in 98% of cases due to the tracts carrying the sperm being blocked. Sexuality remains normal however.