[Chronic stimulation of the immune system in sarcoidosis and monoclonal gammopathy of undetermined significance].

Sarcoidosis is a systemic granulomatous disease which predominantly involves the lungs. Monoclonal gammopathy of undetermined significance (MGUS) characterized by clonal proliferation of plasma cells, can develop into multiple myeloma at a later stage. Although the cause of sarcoidosis remains unknown, the most likely etiology relates to chronic stimulation of the immune system that may result in polyclonal B cell proliferation. In some patients this polyclonal proliferation may develop into a monoclonal B-cell proliferation and induce the appearance of monoclonal gammopathy. In this article, a possible linkage between sarcoidosis and MGUS is raised, based on the case study of a 67-year-old woman and a review of the literature.