Diagnosis of Sarcoidosis

Abstract

The diagnosis of sarcoidosis, a systemic granulomatous disease, is based on a compatible clinical-radiological picture and the histological evidence of noncaseating granulomas. Other diseases mimicking sarcoidosis, mostly infections and other granulomatoses, have to be excluded. There is no single test for sarcoidosis, and the presence of granulomas alone does not establish the diagnosis. Symptoms of sarcoidosis are not specific and can be markedly different according to organ involvement and disease course. Respiratory symptoms and fatigue are the most common symptoms at any stage of disease. Histological confirmation is not needed for Löfgren's or Heerfordt's syndrome and asymptomatic bihilar lymphadenopathy. The radiological staging system is still based on chest radiography, and computed tomography is not mandatory for routine follow-up. (18)F-fluorodeoxyglucose positron emission tomography may be of value in special cases. For assessment of lung involvement and follow-up, pulmonary function tests are necessary with vital capacity being the most important single parameter and diffusion capacity the most sensitive. Bronchoscopy with biopsy is the most common procedure for detection of granulomas, when there is no easier biopsy site like skin or peripheral lymph nodes. Endobronchial ultrasonography-guided transbronchial needle aspiration has replaced mediastinoscopy for evaluation of mediastinal and hilar lymph nodes with a high diagnostic yield. Despite numerous studies, no single biomarker can be reliably used for correct diagnosis or exclusion of sarcoidosis. Genetic testing, despite promising advances, has still not been included in routine care for sarcoidosis patients. The long-term prognosis of sarcoidosis depends on the different organ manifestations: Cardiac or central nervous involvement, together with respiratory complications, is critical. A multidisciplinary approach is necessary for comprehensive care of the sarcoidosis patient.