Cutaneous sarcoidosis: updates in the pathogenesis

Sarcoidosis is a multiorgan granulomatous disease in which the skin is one of the frequently involved target organs. Cutaneous involvement occurs in a third of patients with sarcoidosis and has protean manifestations. More than a century has passed since the initial description of sarcoidosis, but its cause continues to be an enigma. Recent studies have introduced several new insights into the pathogenesis of this disease. The aim of this literature review was to provide a comprehensive overview on the current updates in the pathogenesis of sarcoidosis. This review has revealed that several genetic polymorphisms are associated with an increased risk of developing sarcoidosis, suggesting that genetic susceptibility to sarcoidosis is probably polygenic. Environmental factors may also modify the susceptibility to sarcoidosis. Evidence favouring an infectious aetiology has been accumulating, but the results of studies are conflicting. The current concept is that the pathogenesis of sarcoidosis involves a T-helper-1-mediated immune response to environmental antigens in a genetically susceptible host. The studies carried out on sarcoidosis have largely focused on the pulmonary aspects and have been mainly conducted by respiratory physicians. In contrast, research conducted on the cutaneous aspects of sarcoidosis is comparatively limited. Although tremendous advances have been made, there is a significant gap between the vast knowledge accumulated on sarcoidosis in recent years and the understanding of this disease.