Factitious illness by proxy presenting as anorexia and polydipsia by proxy.

Factitious illness by proxy is a highly pathological form of parent-child relationship. To our knowledge no former case of polydipsia by proxy has been published. The case of a 2-y-old boy suffering from malnutrition due to displacement of maternal anorexia and polydipsia is presented. Child psychiatric evaluation found cognitive delay and psycho-social impairment in the child, as well as a severe mother-child relationship disturbance. Psychological assessment showed a personality disorder with depressive and paranoid features in the mother. The father was described as a schizoid personality. The possible mechanisms of displacement are hypothesized.