Pulmonary sarcoidosis induced by interferon-alpha therapy.

Recombinant interferon-alpha (IFN-alpha) is being increasingly used in the treatment of chronic hepatitis C. It has been recently recognized that IFN-alpha can induce the development of sarcoidosis, presumably through its ability to stimulate the TH1 immune response. IFN-associated sarcoidosis is histologically similar to de novo sarcoidosis and is characterized by tightly compact epithelioid non-necrotizing granulomas. IFN-induced sarcoidosis may be unsuspected clinically, as the most common side effects of IFN-alpha simulate the symptoms of sarcoidosis. It is therefore important for pathologists to be aware of this association and encourage clinicians to carefully review the medication history in cases of pulmonary non-necrotizing granulomatous inflammation where there is a history of hepatitis C, as discontinuation of IFN-alpha can ameliorate the symptoms of sarcoidosis.