Clinical aspects and immune reactions in sarcoidosis*

Abstract

Sarcoidosis is a granulomatous disorder of unknown aetiology, affecting young adults and frequently involving the lungs. The aim of the present review was to give an overview of the clinical aspects in sarcoidosis. The majority of patients recover, but some develop a chronic disease that may result in fibrosis and respiratory failure. Besides the lungs, peripheral lymph nodes, the skin, the liver and the eyes are commonly affected as well. The genetic background, as well as environmental factors, is of importance for developing sarcoidosis. The incidence varies in different populations, in the Nordic countries approximately with 20/100 000 new patients yearly. Sarcoidosis is diagnosed when clinical and radiological findings are supported by histological evidence in the form of non-caseating epithelioid cell granulomas, and when other causes of these features are excluded. Patients in need of treatment are usually treated with corticosteroids, topically or as oral steroids. A clinical effect of immunomodulatory drugs blocking tumour necrosis factor (TNF)alpha has been suggested from several case reports, while two controlled studies showed only minor effects; however, with a tendency to a more pronounced effect on patients with a more severe disease. The immune response in sarcoidosis, with a typical accumulation of CD4+ T-cells to the lungs, indicate the existence of specific antigens in this disease. Recently, antigens derived from infectious agents such as Mycobacteria and Proprionibacterium acnes have come into focus. Lymphocyte populations with immunoregulatory functions have recently been investigated and seem to be dysfunctional in sarcoidosis, opening the possibility of developing new treatment strategies in this disease. Recent technical developments have provided better tools, enabling detailed and more thorough analyses of the inflammatory process in sarcoidosis.