Congenital disorder with secretion of viscous mucus in the air passages and the gastro-intestinal tract. This disease occurs only in children who have inherited the gene for this congenital abnormality from both their parents. The parents are healthy and do not know that they are carriers. The disorder occurs in 1 in 3,000 to 4,000 births. It is caused by an abnormality in the body’s exocrine glands: the sweat glands exude sweat with an unusually high salt content, the pancreas does not function well, and there is thick, viscous mucus in bronchi, clogging the air passages. The seriousness of this abnormality varies from slight to very severe. In almost every case the patient suffers from problems in his air passages and about 80 per cent suffer from indigestion. The first symptoms may be absence of meconium at birth. This may lead to constipation (ileus). Because of poor absorption of fat, the stools appear greasy and are fetid. The child does not grow well, suffers from a lack of vitamins and often succumbs to recurrent attacks of pneumonia, with the added complication of permanent dilation of the alveoli (bronchiectasis). The diagnosis is made by determining the quantity of salt in the sweat. Treatment is directed towards improving food intake, and to prevent or cure any lung infections. A diet rich in albumen and vitamins is prescribed, and pancreatic enzymes which improve digestion are also given. Sprays which dilute the mucus, percussion and breathing exercises are required, as are antibiotics. These measures prolong the patient’s life, although many die young.