Increased serum angiotensin converting enzyme activity in sarcoidosis.

The activity of serum angiotensin converting enzyme (ACE), assayed fluorometrically with the substrate hippuryl-L-histidyl-L-leucine was significantly higher in 116 patients with sarcoidosis than in 415 patients with other diseases--pulmonary and nonpulmonary--and in 58 normal subjects. Serum ACE was elevated in 59% of 46 recently diagnosed, untreated patients with sarcoidosis and was significantly reduced following steroid therapy in three patients with sarcoidosis, but in only one of four patients treated with placebos. The results suggest that elevated serum ACE activity is a valuable, although not absolutely specific, diagnostic indicator of sarcoidosis. It should be stressed that a normal value does not rule out the disease, and that steroid therapy tends to reduce the serum ACE activity.