The relationship between the clinical course of sarcoidosis symptoms and serum angiotensin converting enzyme (ACE)(EC 3. 4. 15. 1) was analyzed through the observation of 51 sarcoidosis patients over the period of more than one year. Before this study, the normal value of serum ACE activity was determined by using normal subjects whose chest roentgenogram, ECG, serum creatinine, serum urea N, serum uric acid, serum cholesterol, serum Na and K, blood pressure, vital capacity and % FVC_1.0 were normal. Serum ACE activity in 311 normal subjects were examined, and the results was 18.7±5.0 nmol/ml/min. The normal range was settled as between 10 and 29 nmol/ml/min. The sarcoidosis patients were grouped into three categories according to their clinical course as follows; (A) sarcoidosis lesions in the chest roentgenogram disappeared within one year,(B) sarcoidosis lesions in the chest roentgenogram remained more than one year with or without little improvement,(C) sarcoidosis lesions in the chest roentgenogram disappeared within a year but then relapsed. In group A (33 cases) serum ACE activity level was 35.9±2.0 nmol/ml/min at the time before treatment. Twenty five of 33 cases showed higher value than 29 nmol/ml/min. The serum ACE level dropped to 22.0±1.3 nmol/ml/min after clearing of chest roentgenogram (p<0.005). In group B (12 cases) the levels of serum ACE activity before and after one year were 41.9±5.3 nmol/ml/min and 34.8±3.2 nmol/ml/min respectively. Eleven of 12 cases showed higher ACE activity than normal range after one year of treatment. In group C (6 cases) a good correlation was observed between the ACE activity and the clinical course.
Through the observation, serum ACE activity was proved to be a good indicator of the sarcoidosis clinical course.