Granulomatous dermatoses comprise a wide range of etiologically and clinically distinct skin diseases that share a common histology characterized by the accumulation of histiocytes include macrophages. While the pathogenesis of these disorders is not fully understood, the underlying mechanism is thought to involve a reaction pattern caused by an immunogenic stimulus. Antigen-presenting cells and the effect of various cytokines play a key role. Our understanding of granulomatous reaction patterns has been advanced by insights drawn from observations of such reactions in patients on immunomodulatory therapy and in individuals with genetic immunodeficiency. Traditionally, a distinction is made between infectious and non-infectious granulomatous dermatoses. The present CME article addresses granulomatous skin diseases for which there is no evidence of a causative infectious agent. Common representatives include granuloma annulare, necrobiosis lipoidica and cutaneous sarcoidosis. Granulomatous dermatoses may be part of the clinical spectrum of various systemic disorders or may be associated therewith. Some neoplastic disorders may mimic granulomatous dermatoses histologically. Given the pathogenetic diversity involved, the clinical presentation, too, is quite varied. Overall, however, each disorder is characterized by typical clinical features. The diagnosis always requires thorough clinicopathologic correlation. Treatment is preferably based on the underlying pathogenesis and frequently involves anti-inflammatory agents. In most cases, however, there is insufficient study data. The dermal nature of these disorders frequently poses a therapeutic challenge, especially with respect to topical treatment.
© 2019 Deutsche Dermatologische Gesellschaft (DDG). Published by John Wiley & Sons Ltd.