Angiotensin-converting enzyme (ACE)

Angiotensin-converting enzyme (ACE) is an enzyme best known for its role in blood pressure control, produced by cells lining blood vessels, particularly in the lungs. As a blood test, though, its main use is quite different: it is used as a supporting marker in sarcoidosis. In sarcoidosis, the body forms small clusters of inflammatory cells called granulomas, most often in the lungs and lymph nodes, and these granulomas produce ACE — so the blood ACE level is often raised when the disease is active and widespread. It is important to understand its limits: ACE is neither sensitive nor specific enough to diagnose or exclude sarcoidosis on its own. Many people with sarcoidosis have a normal level, and it can be raised in other conditions (some infections, liver and thyroid disease, and other granulomatous diseases). Its more useful role is often in following a person already diagnosed with sarcoidosis: a falling level can accompany improvement or treatment response, and a rising level can reflect more active disease, though even here it is interpreted alongside symptoms, imaging and other tests rather than relied on alone.

• Active sarcoidosis — the main association; granulomas produce ACE, so it is often raised in active, widespread disease.
• Other granulomatous conditions — such as certain infections (including tuberculosis) and other lung diseases.
• Some liver and thyroid conditions — can raise it non-specifically.
• Note — a high level supports but does not prove sarcoidosis.

• Normal or low — the expected result, and does not exclude sarcoidosis (many people with it have a normal level).
• A falling level in known sarcoidosis — can accompany improvement or treatment response.
• ACE-inhibitor blood pressure medication — lowers the measured level.