[Angiotensin I-converting enzyme (ACE) for sarcoidosis diagnosis]

Angiotensin I-converting enzyme (ACE) is synthesized by sarcoidotic granulomas defining this enzyme as a diagnosis and prognosis marker of sarcoidosis. This granulomatous disease, a frequent disease with unknown aetiology, is essentially localized in lung and skin, but many other localizations are possible, as well as in nervous system. The diagnosis is based on a panel of clinical, biological and radiological arguments. Serum ACE has a particular interest although its sensitivity and specificity for sarcoidosis are not perfect; ACE can also help to follow this disease either spontaneously or after corticoid therapy. ACE can be measured in bronchoalveolar lavage fluid (BAL) where it better signs the activity of the pulmonary disease than in serum. ACE in cerebrospinal fluid (CSF), and eventually in other biological fluids, allows the diagnosis of sarcoidosis with extra-pulmonary locations. The methods for ACE activity determination are essentially based on the use of polypeptidic synthetic substrates. By varying their nature and the conditions for use various assays were developed for serum, plasma, BAL, CSF and other fluids where ACE can help. The data must be given in a critical manner in function of the actual knowledge on ACE gene, the enzymatic properties of the protein and the limits of sensitivity and specificity of the assays sometimes reserved to peculiar biological fluids.