Shared psychotic disorder or its more common synonym, folie à deux, is a rare clinical syndrome. Its characteristic feature is transmission of delusions from “inducer” (primary patient), who is the “originally” ill patient and suffers from a psychotic disorder, to another person who may share the inducer’s delusions in entirety or in part.1–3 Depending on whether the delusions are shared among two, three, four, five and even twelve people, it is called as folie à deux, folie à trios, folie à quatre, folie à cinq and folie à douze.4
Shared psychotic disorder is mostly observed among people who live in close proximity and in close relationships.5 It is found in parent-offspring, sibling-sibling, or husband-wife constellations. Furthermore, mother-daughter or sister-sister pairs represents fifty percent of the psychotic dyads.6 Rarely all the family members share the same delusions, and this is called folie à famille.5 Additionally, there are case reports of physician-patient folie à deux and even a case involving a dog.7,8
Risk factors include female gender, mental retardation, suggestibility, passivity, histrionic personality traits and suspiciousness, in the secondary patient. Moreover, dependency, ambivalent relationships and repetitive crises have been seen in the family.9–14
All kinds of delusional contents can be seen in this disorder.5
In the present case delusions were shared by a mother and her daughter. The mother, who at first was supposed to have an organic disease, was considered as the dominant psychotic individual. It seemed that her 8-year-old son was a case of delusional disorder by proxy.
A 52-year-old woman was admitted to the emergency room, suffering from weakness, dizziness, and nausea. She complained of difficulty in swallowing solid foods and liquids for 9 days which made her avoid eating and drinking. The patient had the history of loss of appetite and 20 kilograms weight loss during last 9 months. On clinical examination the patient was ill, agitated, and dehydrated, but other physical findings were normal.
The lab data revealed abnormal findings as following: BUN: 100, Creatinine: 3.7, Na: 182, K: 4.2; so she was admitted to the nephrology ward with a diagnosis of acute renal failure and received serum therapy. After several days of close observation, serum therapy, and hydration, serum sodium decreased to normal levels. To evaluate her dysphagia, upper gastrointestinal endoscopy was performed, and showed a mild esophagitis but it could not justify the symptoms and the patient still refused to eat and drink, therefore a psychiatric consultation was requested to rule out anorexia nervosa.
During the interview it was identified that she had a persecutory delusion about food poisoning by her husband’s relatives for about one year. Although her next door neighbors were her husband’s relatives she did not have any relationship with them and she thought they wanted to poison her and her children and they might do this in several ways such as injecting the poison to foodstuff or even in water main. First she only ate fresh food but at last she even avoided drinking water and after a while she became ill and her somatic symptoms such as nausea, weakness, agitation and dizziness were appeared. She said her 22-year-old high school graduated daughter had agreed with her suspicions. She had an 8-year-old son whom she kept at home all the time and did not feed sufficiently.
Her family was invited to gather more information. Her daughter was interviewed, presenting histrionic traits and same delusional beliefs. Her husband was a 55-year-old carpenter. He did not have good relationships with his family and didn’t care about them. He ate his food at work and in spite of the fact that he thought his wife’s beliefs were ridiculous, when his family was starving he did not do anything. Unfortunately he did not give permission for visiting his 8-year-old son. But according to the interview the patient did not feed him sufficiently due to her delusion and when despite of her mother’s warnings, he had eaten something in the school the patient did not let him go to school anymore; so it was supposed that he was a case of delusional disorder by proxy. His condition was followed by a social worker. Regarding delusional disorder diagnosis, the patient was prescribed Olanzapine starting at 5 mg/day, and increased to 15 mg/day. The severity of delusions lessened after three weeks. Despite our plans for more sessions with the family, they refused to come to the hospital after the first session and we could not follow her daughter’s delusions.
In this case patient complained of physical symptoms but the main cause of her symptoms was psychiatric, therefore it’s important to consider possible psychiatric etiologies for atypical symptoms such as sudden onset of dysphagia to liquids and solids in this patient.
Lazarus emphasized that two preconditions must exist before folie à deux can develop: first, an intimate emotional association between the inducer and affected person, and second a genetic predisposition to psychosis, such as blood relations with primary patient11 but shared psychosis is observed among spouses as the second-most prevalent group, that might have not a genetic predisposition to psychosis.3,5
There was no familial history of psychosis in the present family. Patient’s husband, who did not have intimate bond and blood relation with her, did not adopt her beliefs but her daughter who had close relation and genetic connection to her shared persecutory delusions with her.
By proxy condition can be considered when children are forced to manifest their parents’ psychopathologies. For example, in anorexia nervosa by proxy an anorexic mother may restrict her child’s food due to fears of excessive weight in her child, and a paranoid father with a history of psychosis feared that his son was poisoned by breast milk and insisted on checking his son’s hair for mercury in the emergency room.15
Our patient did not feed her 8-year-old son sufficiently due to her delusion and it can be considered as delusional disorder by proxy.