Investigations in Sarcoidosis Lymphopenia is characteristic and liver function tests may be mildly deranged. Hypercalcaemia may be present (reflecting increased formation of calcitriol - 1,25-dihydroxyvitamin D - by alveolar macrophages), paicularly if the patient has been exposed to strong sunlight. Hypercalciuria may also be seen and may lead to nephrocalcinosis. Serum angiotensin-conveing enzyme (ACE may provide a non-specific marker of disease activity and can assist in monitoring the clinical course. Chest radiography has been used to stage sarcoid . In patients with pulmonary infiltrates, pulmonary function testing may show a restrictive defect accompanied by impaired gas exchange. Exercise testsmay reveal oxygen desaturation. Bronchoscopy may demonstrate a 'cobblestone' appearance of the mucosa, and bronchial and transbronchial biopsies usually show non-caseating granulomas, as may samples from the mediastinal nodes obtained by EBUS. Bronchoalveolar lavage fluid typically contains an increased CD4:CD8 T-cell ratio. Characteristic HRCT appearances include reticulonodular opacities that follow a perilymphatic distribution centred on bronchovascular bundles and the subpleural areas. PET scanning can detect extrapulmonary disease. The occurrence of erythema nodosum with BHL on chest X-ray is often sufficient for a confident diagnosis, without recourse to a tissue biopsy. Similarly, a typical presentation with classical HRCT features may also be accepted. In other instances, however, the diagnosis should be confirmed by histological examination of the involved organ. The presence of anergy (e.g. to tuberculin skin tests) may suppo the diagnosis. Ref - Davidsons 23e p632