Case report: We present the case of a 52-year-old man with steroid-dependent ulcerative colitis, needing immunosuppressive therapy with azathioprine. The drug had been started 3 years earlier, but stopped after a few months because the patient reported palpitations, lipothymia, nausea and vomiting. Given the continued steroid-dependent ulcerative colitis and the lack of clinical documentation about a reaction with a dubious relationship to azathioprine, we decided to rechallenge the patient with the drug under clinical monitoring and after informed consent. After starting 50 mg of azathioprine, the patient showed general malaise, nausea and vomiting. An ECG showed atrial fibrillation, and the patient reported that the symptoms were similar to those previously experienced.
Discussion: We have found two other cases of similar onset of atrial fibrillation after azathioprine use, although some confounding elements in these episodes make the possible causal relationship between the drug and this adverse event uncertain.