Azathioprine (Azathioprine®, Imuran®) is an immunosuppressive antimetabolite that is indicated for the treatment of Crohn’s disease, ulcerative colitis, rheumatoid arthritis, systemic lupus erythematosus, dermatomyositis, polymyositis, autoimmune chronic active hepatitis, pemphigus vulgaris, polyarteritis nodosa, autoimmune haemolytic anaemia and chronic refractory idiopathic thrombocytopenic purpura. Erythema nodosum (EN) is a cutaneous disorder that is characterized by tender red nodules, commonly on the shins of the lower legs, and without the formation of pus. The nodules disappear spontaneously within three to six weeks and resolve without residual scarring. However, the nodules can return after a period of time. EN can be triggered by exposure to medicines and micro-organisms but can also occur in combination with systemic diseases. EN is estimated to occur in up to 15% of patients with Crohn’s disease and is linked to an increased disease activity of inflammatory bowel disease. EN is more common in women than in men, and mostly arises in early adulthood. Cases of EN are reported with use of Azathioprine. A total of 4 cases were reported in Netherlands, a further 70 cases on Eudravigilance and 94 on the WHO Global database. In majority of the cases patients recovered 3 weeks after withdrawal of the Azathioprine. Prescribers, while prescribing Azathioprine are therefore urged to inform patients and be on the lookout for EN. For further information please click here.