Genetic predisposition to sarcoidosis: another brick in the wall.

T he belief that a genetic susceptibility to the development of sarcoidosis exists is supported by several lines of evidence: 1) monozygotic twins are more often concordant for the disease than dizygotic twins; 2) sarcoidosis patients are more likely than healthy subjects to report a sibling or parent affected with the disease; 3) prevalence, incidence and severity of sarcoidosis vary widely amongst different races [1–4]. According to our current understanding of the disease pathophysiology, sarcoidosis is not due to defects in a single major gene or chemical pathway; instead, it is a complex disease that likely results from multiple genetic and environmental factors working together, each contributing a relatively small effect and few, if any, being absolutely required for the disease to occur. Genetics is also likely to contribute to the wide variety of clinical presentations and phenotypes observed in sarcoidosis. In this regard, some believe that sarcoidosis represents a family of diseases (sarcoidoses), including, among others: Löfgren syndrome, which is defined as the acute onset of fever, erythema nodosum, bilateral hilar lymphadenopathy and polyarthralgia; non-resolving/progressive lung disease; and granulomatous uveitis, each with potentially distinct genetic associations [5]. Berylliosis could also be considered as a subset of the broad grouping ‘‘sarcoidosis’’.