ACE and Erythema nodosum: Clinical features (e.g., erythema nodosum, uveitis, or changing scar due to localization of granulomas), biochemical markers (e.g., elevated serum angiotensin converting enzyme (ACE), serum or urine calcium, or lymphocytes in the bronchoalveolar lavage fluid), and abnormalities/changes in imaging (chest radiography, CT, or MRI) are conventionally used to assess (change of) disease activity.