ABSTRACT
Although a large number of studies have reported the causes of the exacerbation of ulcerative colitis (UC), the effect of influenza vaccination on the relapse of UC has not been reported. We experienced a case of prompt exacerbation of quiescent UC due to influenza vaccination. A 39-year-old woman was diagnosed as UC 4-years ago and was well controlled with oral mesalazine. She experienced abdominal pain and frequent bowel movements with hematochezia 3 days after the vaccination. On admission, laboratory findings showed elevated erythrocyte sedimentation rate and C-reactive protein. Sigmoidoscopy showed marked edematous mucosa on rectum and sigmoid colon with fine ulceration and spontaneous bleeding. She recovered from the exacerbation of UC after steroid treatment. Vaccination should be administered to the patients with inflammatory bowel disease with the caution of its possible side effects.