Azathioprine-Induced Tremor: A Rare, Dose-Dependent Side Effect of Azathioprine in a Patient With Active Crohn Disease

To the Editors, The thiopurine analogue azathioprine has an important role in the treatment of inflammatory bowel disease (IBD). As monotherapy, it can be used as a steroid-sparing agent for maintenance of remission. The SONIC and SUCCESS studies have proven the enhanced efficacy of an azathioprine and infliximab combination in achieving clinical remission and mucosal healing in Crohn disease and ulcerative colitis, respectively.1, 2 Azathioprine reduces the immunogenicity of infliximab, resulting in higher infliximab levels and lower rates of antidrug antibodies. A female patient aged 45 years with active recently diagnosed Crohn disease was admitted to our department. She had almost 10 bowel movements per day, abdominal pain, low-grade fever, and severe iron deficiency anemia. Endoscopy revealed multiple deep ulcers of the colon and terminal ileum. Combination therapy with infliximab and azathioprine was initiated after a course of steroids. Azathioprine was initially given at a dose of 50 mg per day without any adverse effects. Two weeks later, the dose was increased to 100 mg per day.