Sarcoidosis: correlation of HRCT findings with results of pulmonary function tests and serum angiotensin-converting enzyme assay.

We examined correlations between findings on chest high resolution computed tomography (HRCT), pulmonary function and values of serum angiotensin converting enzyme (ACE) in 25 patients with sarcoidosis. The most frequent CT features were small nodular opacities. The small nodules, representing the confluence of epithelioid granulomas, are strongly correlated with peribronchovascular, perilobular, and centrilobular lesions, where there is an abundance of lymphatic plexus. This strongly suggests the importance of the lymph vessels in the pathogenesis of sarcoidosis. The pulmonary functions tests showed obstructive defects in 6 and mixed-type defects in 2 of the 25 patients. Furthermore, an elevation of V50/V25 ratio suggesting small-airway disease was detected in many patients who showed normal values of FEV1.0% and %VC. This fact indicates that small-airway disease was manifested earlier in sarcoidosis patients. Statistically significant negative correlations were found between visual score and %VC, %FVC, FEV1.0%, %TLC, and %DLco, but there was no significant correlation between visual score and serum ACE. ACE is derived from granuloma-forming epithelioid cells, and the activity of ACE decreased rapidly in mature granulomas. Epithelioid cells in the mature granulomas which can be recognized on HRCT scan have stopped or are about to stop the release of ACE. In this study, serum ACE activity was found to be elevated and correlated with %V25 and V50/V25 at an early stage of the disease. The results of this study provide meaningful insights into the process of sarcoidosis in lung.