Arch Dis Child 89 (11): 1043 - 1048, 2004. doi: 10.1136 / adc.2003.031740 Key Points BRUE (brief, resolved, unexplained event) is defined as an episode of cyanosis or pallor, abnormal breathing, abnormal muscle tone, or altered responsiveness in an infant < 1 year old, with no identifiable cause, and based on the clinician's characterization of the event and not on a caregiver's perception that the event was life-threatening.