CROHNS-DISEASE, SARCOIDOSIS AND RHEUMATOID-ARTHRITIS - EVIDENCE FOR MYCOBACTERIAL ETIOLOGY

The pathogenesis of Crohn's disease, sarcoidosis and rheumatoid arthri tis involves immunopathology that may be caused by a mycobacterial inf ection. Both Crohn's disease and sarcoidosis are granulomatous disease s with some similarities to forms of tuberculosis. Mycobacterium parat uberculosis has been specifically isolated from Crohn's disease tissue by independent laboratories. However, polymerase chain reaction (PCR) studies for detecting mycobacterial DNA in Crohn's tissue have failed to produce consistent results, No specific agent has been isolated fr om sarcoid tissue, but PCR studies have implicated Mycobacterium tuber culosis. Again, inconsistent results have been obtained from independe nt laboratories. Animal models of adjuvant arthritis have been shown t o involve T cells that respond to the mycobacterial 65 kDa heat shock protein. Patients with rheumatoid arthritis have also been shown to ha ve mycobacteria-reactive T cells in their joints but it is unclear whe ther this is specific to the disease. The involvement of mycobacteria in any of these diseases remains unproven.