RESUMO
Objective: To describe a case of an obese child whose weight gain was related to the Munchausen Syndrome by proxy (MSP). Methods: This is a case report including information regarding the child's clinical history and the mother's behavior. The common features of the syndrome are confronted with the description of the case, seeking to demonstrate the similarities. Results: The description ratifies the diagnosis based on the signs and symptoms presented by the child (<5 years old, frequent contacts with health system, symptoms witnessed only by the mother, confusing findings, not helped by treatments, emotionally distant father) and the attitude of the mother (concerned, interested in procedures, comfortable in the medical setting, higher medical knowledge, hostile when thwarted). Conclusion: The case presented points to a new etiology, the MSP, to be considered within the set of factors currently known to cause and maintain obesity in childhood.