The differential diagnosis of acute abdominal complaints is challenging in Crohn's disease. This is particularly true in patients in remission induced by biological therapy. In addition to the acute relapse of Crohn's disease, other common causes, such as acute appendicitis exhibiting similar and often atypical course, should be taken into consideration irrespective of the age. An ileocecal flare-up is unlikely to occur in patients with perianal Crohn's disease in remission induced by infliximab even if laboratory and radiological findings point towards this diagnosis. We report the case of a middle-aged woman in remission induced by infliximab who developed acute abdominal symptoms due to perforated appendicitis. Orv Hetil. 2018; 159(10): 405-409.