PT - JOURNAL ARTICLE AU - Azhar Abbas Malik AU - Haider Abbas AU - Zin Mar Oo AU - Zerlene Lim TI - CDK4/6 inhibitor-induced colitis: a case report and review of the literature AID - 10.1136/bcr-2021-242766 DP - 2021 Jul 01 TA - BMJ Case Reports PG - e242766 VI - 14 IP - 7 4099 - http://casereports.bmj.com/content/14/7/e242766.short 4100 - http://casereports.bmj.com/content/14/7/e242766.full SO - BMJ Case Reports2021 Jul 01; 14 AB - A 72-year-old woman with metastatic ER/PR-positive breast cancer who had been on ribociclib and letrozole for 1 year developed severe life-threatening colitis. She presented to emergency department with features of acute abdomen and diarrhoea. The diagnosis of colitis was confirmed radiologically as well as by histopathological examination of the biopsy specimen and the patient clinically improved after withholding ribociclib and receiving corticosteroids compatible with ribociclib-induced colitis. The mechanism of injury in CDK 4/6 inhibitor-induced colitis is unknown but may be related to recruitment of inflammatory cells. Whether the development of colitis is associated with tumour response is an interesting and unanswered question.