[An unusual cause of a decline in general health in a very old person].

Humans are accidental intermediate hosts and a dead-end for the echinococcosis parasite. No cases of hydatid echinococcosis (hydatid cyst) have ever been described in a French-born very elderly person, who has never been out of France. We report the case of a 90-year-old man hospitalised following a decline in his general health and the discovery of a liver mass on the CT-scan. The abdominal palpation was painless, and no mass was felt. Biological tests revealed hypereosinophilia, a mild inflammatory syndrome, a slight increase in the immunoglobulin E level, and positive serology for Echinococcus granulosus. A diagnosis of hydatid echinococcosis due to Echinococcus granulosus was made given the liver mass on the CT-scan, the positive serology and the hypereosinophilia. Management consisted of watch and wait. This observation is interesting because it was a case of an autochthonous hydatid cyst of an unexpected discovery in a very elderly patient. Indeed, even though the discovery was classical, the clinical presentation was singular because of the context.