Risk of malignancy in myasthenia gravis patients exposed to azathioprine therapy for a median period of 3 years

The long-term risk of malignancies in patients treated with immunosuppressive drugs is a concern among patients and physicians. Patients with myasthenia gravis (MG) respond well to azathioprine (Aza) but many require longterm treatment. The therapeutic effect is presumably largely due to reduced proliferation of actively dividing lymphocytes; however, the benefit of suppressing autoreactive lymphocytes may theoretically result in a concomitant reduction of immunosurveillance and thereby increase the risk of cancer. Many have assessed the malignancy risk in autoimmune diseases such as inflammatory bowel disease (IBD) and rheumatoid arthritis (RA), but these may have their own inherent risk such as colorectal cancer in IBD or lymphoma in RA.1,2 Few studies have been published related specifically to Aza exposure and cancer risk in MG.3,4 This report concerns the incidence of cancer in a South African MG cohort specifically assessing the Aza dose and the duration of treatment