CYSTIC FIBROSIS



Cystic fibrosis is a common generalized disor­der of exocrine gland function, which impairs clearance of secretions in a variety of organs (Table 19-4], This autosomal recessive disorder occurs in about 1 in every 2000 white births. The underlying defect is unknown, but the pulmonary pathophysiology is similar to other causes of bronchiectasis, with tenacious mucus and im­paired ciliary function resulting in recurrent in­fections, chronic inflammation, and bronchial wall destruction.

The disease is usually manifest in childhood, often with gastrointestinal symptoms, particu­larly steatorrhea and bowel obstruction (Table 19-4). However, the pulmonary features pose the biggest problem. Classically, Staphylococcus au­reus in childhood and the mucoid strain of Pseu-domonas aeruginosa in later years cause recurrent respiratory infections that are particularly diffi­cult to treat because of chronic colonization of the airways. Definitive diagnosis requires the finding of an elevated concentration of sodium or chlo­ride in the sweat. When correctly collected and analyzed, levels above 60 mEq/L in children or 80 mEq/L in adults are diagnostic in the proper clin ical setting. The course is usually one of gradual but progressive respiratory failure. Some patients with milder disease escape diagnosis until their late teens or even early 20’s. These patients usu­ally have minimal extrapulmonary problems and have been carried for years with a diagnosis of asthma or even just recurrent bronchitis. The true diagnosis is usually made when the disease wors­ens or problems with another organ system, such as the discovery of infertility, lead to a more com­plete evaluation. Recent improvements in anti­biotics, nutritional therapy, and supportive care, however, have improved the prognosis such that the median survival has increased from less than two years in the 1940’s up to more than 20 years today.





CYSTIC FIBROSIS