Genetic aspects in sarcoidosis.

Sarcoidosis is an immune-mediated, multiorgan, granulomatous disorder thought to be triggered by an intricate combination of environmental and genetic factors. Two robust lines of evidence support the hypothesis of a genetic component in the pathogenesis of sarcoidosis: racial variation in its epidemiology and familial clustering of cases. The relationship between epidemiology and environmental factors affecting variations in sarcoidosis incidence/prevalence and presentation are reviewed, as well as strategies to be pursued in the search for susceptibility genes for the disorder. Pathogenic processes leading to sarcoid granuloma formation and maintenance have prompted investigators interested in the genetics of sarcoidosis to focus mainly on major histocompatibility complex genes, and indeed a remarkable amount of data has been accumulated during the last two decades. Whilst in contrast with some autoimmune disorders a clear association between human leukocyte antigen (HLA) and sarcoidosis is still a controversial issue, there is, however, a general agreement that some HLA genes are related to phenotypic variations of the disease. Some genetic investigators have focused on T-cell receptor genes, immunoglobulin genes, angiotensin converting enzyme gene, chemokine genes and others. From a review of studies performed in different racial and ethnic groups, a reasonable suggestion arises that genetic factors are the major determinant in the racial variations in the epidemiology of the disorder. This assumption is, however, so far limited by lack of studies considering both genetic and environmental factors simultaneously.