Angiotensin converting enzyme. IV. Changes in serum activity and in lysozyme concentrations as indicators of the course of untreated sarcoidosis.

The mean values of serum angiotensin-converting enzyme (ACE) activities and lysozyme (LZM) concentrations measured during different phases of sarcoidosis coincided well with the clinical evaluation of the state of the disease. However, both enzymes, especially LZM, decreased before improvement was detected. Changes in these enzymes were in accord with the simultaneous clinical development in three fourths of cases. Incompatibility between clinical observations apnd LZM fluctuations was most frequently seen during active stable or inactive disease. LZM often decreased during the active stable phase and fluctuated irregularly during inactive disease. During the former phase LZM decrements possibly reflect decreasing activity of granulomatous macrophages and, in fact, precede detectable improvement. During inactive disease, on the other hand, cells were not connected with the disease process dominate LZM production. ACE changes paralleled the clinical development more often than corresponding LZM changes during stable sarcoidosis. This may have been misleading and due to a delayed reaction of serum ACE, compared with LZM, inreflecting the activity of granylomatous cells. This delayed reaction was also observed in connection with erythema nodosum. Stable ACE activity during inactive sarcoidosis indicated the usefulness of measurements when trying to predict a relapse. We conclude that ACE may be a secondary feature of sarcoidosis rather than a primary funtion of macrophage activity.