Clinical correlations of plasma angiotensin converting enzyme (ACE) activity in systemic sclerosis: a longitudinal study of plasma ACE level, endothelial injury and lung involvement.

Lung involvement was studied by perfusion scan, ventilation scan, pulmonary clearance rate of 99mTc DTPA and pulmonary function tests in 20 patients with systemic sclerosis (SSc). Decreased plasma angiotensin converting enzyme (ACE) activity and increased levels of von Willebrand Factor Antigen (vWF:Ag) were found in all patients with SSc. The relationship between ACE levels and lung involvement was not statistically significant, however levels of vWF:Ag correlated with parameters of lung vascular alterations. An inverse relationship between the reduced ACE levels and ESR was found. It is likely that ACE levels reflect the inflammatory aspect of the disease. Further studies of ACE synthesis, release and inhibition are needed to determine the mechanism of the observed decreased activity in SSc.