Etiology of sarcoidosis

The cause(s) of sarcoidosis is unknown. Sarcoidosis seems to result from exposure of a genetically susceptible subject to a specific environmental antigen(s). From biopsy samples of lymph nodes from patients with sarcoidosis, Propionibacterium acnes has been isolated in culture, and many genomes of P.acnes or P.granulosum have been detected by quantitative PCR. Antigen-specific mitogenic responses of peripheral blood mononuclear cells were induced in sarcoidosis patients but not in healthy controls, when recombinant proteins from a propionibacterial trigger factor were used as stimulators. Sarcoidosis may arise from a Th1 immune response to one or more antigens of propionibacteria in an individual with a hereditary or acquired abnormality of the immune system.