Side-effects of azathioprine treatment in rheumatoid arthritis: analysis of 10 years of experience.

Our experience with azathioprine in the treatment of rheumatoid arthritis covers ten years, during which 91 rheumatoid patients (66 female and 25 male) received this drug, with a median treatment period of 36 months. Total follow-up experience, during and after treatment, was 399 person years. Twelve patients died. The principal causes of death were malignant neoplasm (six patients) and cardiovascular diseases (three patients). The mortality in our patients was compared to that of the general Dutch population by the Standardised Mortality Ratio (SMR). In the male patient group a significant excess of both total mortality and mortality from malignancy was observed. The female patients showed no differences from the general population. In this follow-up study, no lymphoreticular tumours occurred during or after azathioprine therapy.