Treatment with interferon (IFN) can precipitate a variety of inflammatory conditions, including sarcoidosis. Although many other systems can be affected, the clinical picture in this case mostly includes cutaneous and pulmonary symptoms. The prognosis is better than the idiopathic form of the disease, and the most effective treatment is considered the discontinuation of antivirus therapy alone or in combination with corticosteroid administration. The authors present the case of a 36-year-old man who developed sarcoidosis stage I after 2 years of IFNα therapy for polycythemia vera.