Angiotensin converting enzyme. III. Changes in serum level as an indicator of disease activity in untreated sarcoidosis.

The activity of serum angiotensin converting enzyme (ACE) was repeatedly measured together with serum lysozyme (LZM) in patients with untreated sarcoidosis. Changes in the clinical picture were registered using chest X-ray, forced vital capacity (FVC), diffusing capacity for carbon monoxide (DLCO) and appearance of extrapulmonary lesions. During a clinically unchanged period the highest ACE activity and the corresponding LZM value (not the highest value) were used for the calculation. A statistically significant change in ACE was noted when a normal chest X-ray changed to a stage II lesion or vice versa, and when a signficant change in FVC occurred. All other changes were insignificant. On the other hand, statistically significant changes in ACE were found during stable periods according to chest X-ray, FVC or DLCO. ACE is frequently elevated in serum of patients with active sarcoidosis. The fluctuations in activity mostly parallel the clinical course of the disease. The behaviour and metabolism of the enzyme need further investigation. An increased concentration of serum LZM is frequent in patients with active sarcoidosis. The highest LZM values are not always seen simultaneously with the highest ACE values, indicating that they probably express different dimensions of the disturbances in the sarcoid granuloma.