Sarcoidosis is a complex, systemic inflammatory disease that mainly affects adults by the age of 20-40. Most patients suffer from impaired lung function. However, almost every organ can be affected by the typical granulomatous immune reaction. In many cases clinical symptoms disappear within 2 years of disease endurance, but a large proportion of patients suffer from chronic sarcoidosis without a chance of spontaneous remission. Fatal clinical outcomes are often seen in the rather rare instances of cardiac or neural sarcoidosis. Most patients are treated with corticosteroids, no specific therapy exists.
The etiology of the disease is unknown. A bacterial or viral antigen is discussed as the trigger for the sarcoidosis immune reaction in a genetically susceptible individual. This antigen remains to be defined, while a number of genetic risk factors are known, e.g. BTNL2, ANXA11, a locus on chromosome 11q13.1 and, most consistently, several loci in the HLA region on chromosome 6p21. Some risk loci are common for sarcoidosis and other inflammatory or autoimmune conditions, e.g. genetic variation in the IL23R gene locus predisposes also to Crohn´s disease, ulcerative colitis, psoriasis and others. To date, the clinical application of genetic factors is restricted to certain HLA-alleles that support the diagnosis of Löfgren´s syndrome, a benign form of sarcoidosis without lung involvement.