Cystic fibrosis related lung diseases in young adults with minimal impairment.
A small fraction of patients with cystic fibrosis (CF) survive to adulthood with exceptionally mild pulmonary impairment, in marked contrast to the usual natural history of CF. 6 young adults with CF with a high clinical score were studied to assess lung function, roentgenography, bacteriology, and the distribution of ventilation and perfusion. 1 such patient died during the course of the study from a cause other than CF-related respiratory failure, and the autopsy findings were reviewed. Although a few individuals showed normal and near-normal pulmonary function, evidence for mild to moderate obstructive airways disease was present in most tests performed, particularly the maximal expiratory flow between 25 and 75% of vital capacity. The helium dilution technique of determining total lung capacity generally underestimated the values by the technique of roentgenographic planimetry which were within the normal range. Lung scintigraphy revealed matched subsegmental defects in ventilation and perfusion, with 2 subjects showing mismatched defects. The histological findings in the deceased patient were similar to those in infants before the development of pulmonary infection and showed an abnormally thick and uneven basement membrane of the bronchial epithelium. These findings support the view that CF-related lung disease in these patients is qualitatively similar to the early disease in children, but is exceptionally slow to develop in a favored few who nonetheless have greater functional disturbance than their lack of symptoms would suggest.