Pulmonary function tests.

Systemic sclerosis-associated interstitial lung disease (SSc-ILD) is the leading cause of morbidity and mortality in SSc patients. In autopsy studies, up to 70% of the SSc patients show histological evidence of lung involvement. In surgical lung biopsies from SSc-ILD patients, a pattern of non-specific interstitial pneumonia is present in a majority, while usual interstitial pneumonia is found in a more variable proportion of patients. Up to 90% of the SSc patients have lung function abnormalities, especially with respect to gas transfer. Pulmonary function testing, therefore, is a major tool of investigation of lung involvement in SSc.