Cystic fibrosis (CF) is an inherited disorder which affects the body's epithelial cells. Under normal circumstances, certain types of epithelial cells produce mucus and other watery secretions which coat the passageways of the lungs, liver pancreas, urinary tract, reproductive tract, and sweat glands. In cystic fibrosis, however, inherited CF genes cause these epithelial cells to produce secretions that are much thicker than normal.

The symptoms include poor weight gain in spite of a good appetite, deficiencies of vitamins A, D, E, ad K, stools that smell foul and are fat-filled, frequent diarrhoea, 'gas' and repeated respiratory infections, which may lead to shortness of breath, a blue tint to the skin or fingernails, wheezing, or a chronic cough which may produce mucus or blood. CF also results in a 2-year delay in sexual development at puberty. Ten per cent children with CF become diabetic after age 8.

Doctors measure the amount of salt in skin sweat to determine CF.

CF can also be diagnosed by genetic testing performed on a blood sample. This testing will confirm the presence of one CF gene (CF "carrier") or two CF genes (CF illness).

There is currently no way to prevent CF. Children who are newly diagnosed with CF will be started on a modified diet, together with vitamin supplements and doses of pancreatic enzymes. If lung infections are frequent, antibiotics will be given. In about 50 per cent of cases, full-blown CF is fatal by age 30.