We describe the case of a 69-year-old male with Crohn's disease (CD), treated with infliximab and undergoing intestinal resection. The surgery and postoperative period were unremarkable, with no CD-related symptoms. Two months after surgery and two weeks after the introduction of infliximab, he was admitted due to acute onset diffuse abdominal pain, hematochezia and arthralgia. On physical observation on admission, he showed signs of arthritis of the left knee. Laboratory tests revealed renal failure with nephrotic proteinuria, slightly low complement (C3) and IgA elevation. Remaining autoimmunity and viral panel were negative. Abdominal examination showed duodenum and thickening of the proximal wall of the jejunum. Biopsies excluded active CD. Colon and ileum mucosa were normal. The patient met EULAR criteria for Henoch-Schönlein purpura and was started on prednisolone with response. Although no clear trigger was pointed out, we switched anti-TNF to ustekinumab. We present this case given its endoscopic exuberance, and because of the high index of suspicion to make the diagnosis in adult patients with previous inflammatory bowel disease. The distinction between this vasculitis and CD is of utmost importance, given the therapeutic implications.