Four years after the first episode, relapse of the primary rectal lesion was found. of patients develop nivolumab-associated colitis (Common Terminology Criteria for Adverse Events v4.0; CTCAE, any Grade), and less than 10% of patients have severe colitis (Grade 3 or 4 4). Nivolumab-associated colitis generally occurs one to three months after starting nivolumab therapy (2). As irAEs can occasionally be lethal, the readministration of nivolumab after a severe irAE has been controversial. We herein statement a case of restarting nivolumab after recovery from nivolumab-associated colitis. Case Statement An 82-year-old Japanese woman was admitted to our hospital with intermittent severe abdominal pain. She experienced a history of malignant rectal melanoma treated with transanal tumor resection and 6 subsequent cycles of adjuvant chemotherapy (dacarbazine, nimustine, and vincristine: DAV) 15 years earlier. Four years after the first episode, relapse of the primary rectal lesion was found. With transanal tumor resection and DAV therapy, periodical gallium scintigraphy confirmed no tumor residue. She had been followed-up for three years after the relapse and experienced finished her periodical checkups seven years earlier. Four months before admission, she noticed bloody CI994 (Tacedinaline) stool. Colonoscopy revealed the recurrence of rectal melanoma at the primary site with pathological confirmation, and computed tomography (CT) detected multiple lesions of para-aortic lymph nodes, lung, liver, and the first lumbar vertebra. We detected no other malignancy. Given the recurrence at the rectal main site and simultaneous multiple lesions on CT, she was diagnosed with recurrent melanoma with multiple metastasis to the liver, lung, para-aortic lymph node, and first lumbar vertebra. Her Eastern Cooperative Oncology Group overall performance status was 0. She was administered nivolumab (2 mg/kg) every 3 weeks. After completing six cycles of nivolumab, she designed severe abdominal pain and loose bloody stool twice per day and was referred to our hospital. She experienced a sudden onset of a fever (38.1) the day before CI994 (Tacedinaline) admission to our institution. A physical examination revealed abdominal tenderness from your left hypochondriac to the lower quadrant region. Laboratory findings showed an increased white blood cell count (12,400/mm3, neutrophils 87%), C-reactive protein level (CRP, 23.0 mg/dL) and decreased hemoglobin (9.7 g/dL). Nuclear antibodies MAP2K2 and antineutrophil cytoplasmic antibodies were unfavorable. Contrast-enhanced CT on the day of admission showed that this colonic wall from your cecum to the transverse colon was markedly edematous and thickened (Fig. 1A), which is not consistent with ischemic colitis, as this typically occurs in a localized region, such as the splenic curvature, due to a reduced blood supply from the major arteries. We excluded infectious colitis due to the following clinical findings: Both blood and stool cultures were unfavorable for pathogenic bacteria, and CI994 (Tacedinaline) serum screening of cytomegalovirus (CMV) and Epstein-Barr computer virus (EBV) were unfavorable. These clinical findings and the history of nivolumab therapy suggested an association between colitis and nivolumab therapy. Colonoscopy could not be performed because of severe abdominal pain and the risk of perforation at that time. Colonoscopy was therefore planned after the amelioration of her symptoms. Open in a separate window Physique 1. CT image. (A) The cecal wall was CI994 (Tacedinaline) markedly thickened (arrowheads) at the onset of colitis on the day of admission. (B) The thickened cecal wall was improved on day 21 of corticosteroid treatment. (C) Recurrence of thickened cecal wall three weeks after corticosteroid treatment was discontinued. The patient discontinued nivolumab and was immediately treated with intravenous prednisolone 2 mg/kg/day combined with antibiotics according to the manufacturer’s management guidelines (1). Her abdominal tenderness was relieved in the next day and completely ameliorated after one week. The blood in her stool was resolved, and loose stool once a day was observed until six days after admission. Her hemoglobin level improved from 9.7 g/dL to her baseline level (12 g/dL) after1 week without blood transfusion. Prednisolone was gradually tapered every three days. As her symptoms were ameliorated, colonoscopy was performed on day.