Low prevalence of SAD has also been reported by cithers that concluded that cigarette smoking seems to have a major additive effect on the prevalence of obstructive disease in systemic sclerosis. Steen et al found 28 percent of smoking patients vs 12 percent of nonsmoking patients having obstructive lung disease. Bjerke et al, also studying 39 patients with scleroderma, refer to only 2 of 22 nonsmokers and 8 of 17 smokers with SAD. They noted that such a functional disturbance is rare in nonsmoking patients, even when moderate pulmonary involvement is present in scleroderma. The most frequent abnormality in their patients was an increase of static elastic recoil pressure, suggesting that the peribronchial fibrosis does not limit airflow. This is possibly due to a compensatory tethering effect exerted by the stiffened alveolar wall in patients with scleroderma.
Prolonged therapy with D-penicillamine has been reported in association with improvement in Deo but not in FVC. So the use of D-penicillamine in four of 31 studied patients does not seem to influence the prevalence of SAD in our study. Obliterative bronchiolitis, caused by D-penicillamine, does not appear to be a frequent side effect in scleroderma. Since only one of our patients with SAD has been treated with it, we think that the prevalence of SAD has not been affected by D-penicillamine toxicity.
In conclusion, the functional data of our patients, as well as the comparison between these nonsmoking patients and age- and sex-matched control subjects, suggest that SAD is neither an early nor characteristic feature of systemic sclerosis. This finding, when present, is not correlated with the severity of the restrictive disease, which is the cardinal feature of pulmonary involvement in systemic sclerosis.