Cystic fibrosis is the most common autosomal recessive genetic disease in the Caucasian population, affecting about 1 in every 2,500 individuals. The condition is caused by a defect in the CFTR gene, which encodes a protein whose function is to transport chlorine through epithelial cells. Under normal conditions, particular cells lining the airways secrete mucus along with a watery fluid that decreases its density. In cystic fibrosis, secretion of aqueous fluid is greatly reduced, so mucus becomes very thick and difficult to remove from the airways even with the most vigorous coughing.with the risk of obstruction of the respiratory, pancreatic and biliary tracts, with progressive damage to the organs involved (bronchi, lungs, pancreas, liver). The disease may manifest itself more or less early on with respiratory impairment (pertussis cough, persistent catarrhal cough, recurrent bronchitis and bronchopneumonia, chronic bronchopneumopathy) and/or with digestive disorders secondary to pancreatic insufficiency (malabsorption syndrome, stunted growth). Less frequently, and depending on the age of the patients, other clinical pictures may also be present (meconium ileus, hepatopathy, diabetes, sinusitis, nasal polyposis, osteoporosis). The advanced stages of the disease can be characterised by the onset of serious complications (cardio-respiratory failure, pneumothorax, haemoptysis, biliary cirrhosis). The diagnosis can be suspected at birth by various methods, but the most common is the trypsin assay in blood taken on the fourth day of life. Diagnostic certainty is provided by the sweat test, which shows a high concentration of chlorine and sodium in the sweat itself, and/or by the identification of gene mutations. In families at risk, prenatal diagnosis is possible in the first trimester of pregnancy with chorionic villus sampling.