COMMENTARY

Infectious Antigens May Play a Role in the Pathogenesis of Sarcoidosis

Wonder Drake, MD

Disclosures

December 22, 2008

 


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Sarcoidosis is a granulomatous disease of unknown etiology which involves the lungs, skin, lymph nodes, and eyes. Syndromes with similar pathologic and immunologic features to sarcoidosis, such as tuberculosis and chronic beryllium disease, illustrate that granulomatous disease may or may not have an infectious cause.

Since its earliest descriptions, infectious agents have been postulated to have a role in sarcoidosis pathogenesis. Studies of sarcoidosis T-cell receptor gene expression suggest an MHC-restricted antigen-driven process. A recent study from Johns Hopkins Hospital found evidence of humoral responses to mycobacterial protein katG in approximately 50% of sarcoidosis patients and evidence of katG proteins in 55% of their tissue specimens. These findings were significantly distinct from PPD- healthy volunteers.[1] Studies of Polish sarcoidosis subjects found evidence of mycobacterial heat shock protein in sarcoidosis granulomas.[2]

Cellular immune responses against mycobacterial antigens have been noted in the lungs and peripheral blood of sarcoidosis subjects residing within the southeastern United States.[3] There has also been evidence of mycobacterial DNA in their granulomas.[4] Japanese sarcoidosis researchers continue to report evidence of propionate DNA in sarcoidosis granulomas.[5]

Does this mean sarcoidosis is an infection? No. However, these provocative findings do support continued investigation of the role of microbial antigens. They could reflect persistent microbial proteins or a replicating organism. The latter would support a trial of antibiotics as a potential therapeutic in the sarcoidosis armamentarium. Currently, immune suppression remains the primary treatment modality.

That's my opinion. I'm Dr. Wonder Drake, Assistant Professor of Medicine at Vanderbilt University in Nashville, Tennessee.

 


 

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