Cystic fibrosis and bronchial hyperreactivity. Concomitant defects or cause and effect?

Bronchial reactivity and lung-function tests were measured in 19 young adults with cystic fibrosis. There was moderately severe airways obstruction without hyperinflation, and mild hypoxaemia with normocapnia. Bronchial reactivity (fall in FEV1 after the administration of methacholine aerosol) was increased in about two-thirds of patients, and was markedly enhanced in nearly half of them. It was considered that the airways obstruction characteristic of cystic fibrosis can have a reversible element, and that this may provide a rationale for the use of bronchodilators in some patients. Although bronchial hyperreactivity in cystic fibrosis could represent concomitant underlying defects, a more attractive suggestion is that the chronic inflammation of cystic fibrosis has, in turn, led to acquired bronchial hyperreactivity.