Abstract. Interferon-α (IFN-α) is currently used in the treatment of various malignant tumours. Development of different autoimmune disorders has been reported in some patients during IFN-α therapy. Systemic lupus erythematosus (SLE) after treatment with IFN-α has not been described, although a majority of SLE patients have demonstrable serum levels of IFN-α, which correlate with disease activity and have been suggested to be of pathogenetic significance.
In this paper we describe a patient with a malignant carcinoid tumour who developed a SLE-like syndrome during treatment with leucocyte IFN-α. The patient developed myalgia and low grade arthritis in multiple joints together with a high titre of antinuclear antibodies (ANA) and anti-dsDNA antibodies. After the treatment was stopped, the symptoms subsided although a moderate ANA titre persisted. However, the tumour continued to regress despite cessation of IFN-α therapy. During a short course with recominant IFN-α the syndrome relapsed, supporting the concept that the SLE syndrome was precipitated by IFN-α. A connection between IFN-α treatment, the induced autoimmune disorder and regression of the carcinoid tumour is suggested.