[Delusional parasitic infestation and folie à deux: case report].

Shared psychiatric disorder (folie deux) is a rare condition. But its prevalence can be 5-25% in patients with delusional parasitic infestation. We report the a case of a 62 years-old female with psychotic symptoms. For 15 years, she has lived with her younger sister. Since the patient was well-controled, her sister interrupted her antipsychotic drug administration. So, the patient initiated delusional parasitic infestation accompanied by visual hallucinations. Her sister, who did not have psychiatric history, initiated to believe that the patient was really infested. Moreover, she started to believe that was infested by the patient. This case report aims to discuss the relation between folie deux and delusional parasitic infestation.