During a training session for the university diploma of Mountain medicine delivered by University Sorbonne Paris Nord for medical doctors, one of the participants developed signs of maladaptation to high altitude at 3 600 m, the severity of which was incorrectly interpreted. Information was sparingly given by the patient (an anesthetist) to several of his colleagues and no one was in charge to collect clinical data, take a history, and provide appropriate treatment. The combination of the absence of designation of a supervising doctor and the difficulty of communicating with the patient led to a lack of coordinated management and to an evolution of the symptoms towards severe acute mountain sickness. Fortunately, the very rapid management of the patient and a rapid helicopter evacuation, as soon as the symptoms worsened towards the onset of a suspected high altitude cerebral and/or pulmonary edema, allowed rapid resolution without sequelae. Environmental, medical, psychological, and managerial factors led to this Expert Group Syndrome.