Granulomatous Diseases Mimicking Sarcoidosis

Granulomatous diseases are not infrequent in daily clinical practice. Granulomas are the expression of a sufficiently (partial) functioning immune system. Many diseases, with different etiologies (infection, autoimmunity, inflammatory, foreign bodies, malignancy, metabolites, chemicals, etc.) can cause granulomatous manifestations. The differential diagnostic process of a granulomatous disease should always be made in an interdisciplinary cooperation. Diagnostic procedures should be oriented to the clinical symptoms suggestive microbiological studies, and radiography but the diagnosis of a granulomatous disease should always be confirmed by histopathology when possible, sampling for histology or cytology. From a pathogenic point of view, they are divided into noninfectious and infectious granulomas. In the case of proven granulomatous inflammation, an infectious etiology should first be excluded (including mycobacteria, parasites, and fungi). From a clinical point of view, it is useful to separate granulomatosis into localized and disseminated forms, although this distinction can be sometimes artificial. Three types of localized granulomatous lesions can be distinguished: infectious granulomas, palisaded granulomas (granuloma annulare, necrobiosis lipoidica, and rheumatoid nodules), and foreign body granulomas. Disseminated granulomas can be divided into infectious, in particular tuberculosis, and noninfectious forms (autoimmune, neoplasia, etc.).