Delusional parasitosis with folie à deux: A case series.

Delusional parasitosis (DP) is characterized by single hypochondriacal delusion in which patient feels he/she is infested with insects. The authors present a case series of three cases of DP with shared psychotic disorder (folie à deux) in which one individual developed a delusional belief in the context of a close relationship with another person or people who already had an established delusional idea. All patients of DP were assessed in the outpatient department of Psychiatry of a tertiary care hospital. Diagnosis of DP was made on detail clinical history and supporting clinical findings. All our primary cases had DP and the accompanying relatives of our patients had folie à deux as they shared the belief of parasite infestation which was firm and persisted despite evidence to the contrary. The primary cases of delusional parasitosis responded well to oral risperidone. The intensity of the belief in the secondary person also reduced with improvement in the symptoms of the patients.

Delusional parasitosis (DP) is characterized by a belief in which patient feels he/she is infested with insects.[1] Dermatologists often find it difficult to treat, as it is not a disease of the skin, but a psychotic disorder where the person's belief is absolutely unshakable and often carries a high level of psychosocial morbidity.[2] Another individual may share this delusion due to a close relationship with the person known as “folie à deux” which is seen in about 15-25% of the cases.[345] The authors present a case series of DP with shared psychotic disorder (folie à deux), which are rare phenomena with a difficulty in treating the individuals sharing the delusion.

CASE REPORTS

Case 1

A 55-year-old female patient came with the complaints of itching and removing skin debris due to lice infestation since 3 years. She applied camphor oil all over the body, collected skin debris in containers and burnt it to kill the lice. Erythematous patches over scalp and multiple scratch excoriations marks were seen over the whole body. The patient in reality had no lice infestation and had been treated by the dermatologist for the same. Her mother apart from sharing her daughter's belief did not have any psychiatric symptoms as per our clinical interview and a detailed history. The patient was started on tablet risperidone 2 mg increased to 6 mg over 3 months with amelioration of symptoms. The patient's mother did not cooperate with us for the suggestion of separation from her daughter, and both were later lost to follow-up.

Case 2

A 37-year-old female patient complained of insects crawling over her body, itching and disturbed sleep since 6 months. She applied oil all over her body multiple times a day and collected the skin debris in the water to kill the insects. Multiple scratch excoriations marks over the extremities were seen. Patient's mother in law also believed her though she denied seeing any insects and would help the patient in applying oil to reduce the itching and kill the insects by rubbing the skin. Clinical evaluation of both the patient and her mother in law did not reveal any other psychopathology. The patient was prescribed tablet risperidone 2 mg increased to 4 mg over 3 months with a near total resolution of symptoms with her mother in law being amenable in her behavior toward us.

Case 3

A 67-year-old male patient complained of itching and infestation of the skin with insects all over his body since 2 years. He felt that when the insects or mosquitoes would sit on his skin they would burrow and go under the skin. Hence he and his wife spent most of the time of the day in squatting away mosquitoes, so as to reduce infestation by them. He had a past history of ischemic heart disease and diabetes since 15 years and was on medication. His wife shared his belief and had often told the dermatologist to give medication to kill the insects. She attributed that it was possible for insects to be in the body as people were dying due to various ailments caused by insects and parasites. She refused to accept our explanation that there were no insects in her husband's body and, in fact, got angry with us for being so unsympathetic. The patient was treated quite extensively by the dermatologists. All other investigations were normal, and his blood sugars were maintained. Both did not reveal any other psychopathology. The patient was prescribed tablet risperidone 2 mg increased to 3 mg over 3 months with a reduction in itching. His wife was happy with the reduction in her husband's preoccupation and symptoms.

DISCUSSION

All our patients were investigated and treated adequately with other skin conditions ruled out by the dermatologist before referral to the psychiatrist and a diagnosis of DP was considered as per Diagnostic and Statistical Manual of Mental Disorders Fourth Edition Text Revision criteria.[3] Female preponderance in patients and their relatives sharing the belief and belonging to the middle age group was in keeping with the findings of other researchers.[56]

Delusional parasitosis can be caused by Vitamin B12 deficiency, pellagra, hepatic and renal disease, diabetes mellitus, multiple sclerosis, and leprosy.[7] DP has a high burden of psychosocial morbidity with self-harming behavior and suicide, but none of our patients demonstrated any other psychopathology. DP follows a chronic course, has an insidious onset[8] affecting the trunk, scalp, genital areas, and eyelids.[6] The “matchbox sign” where they bring things like dead skin, flakes etc., in a box to show the doctor the proof of their illness[910] or spray pesticides in the house, change clothes frequently or take a bath repeatedly was also noted in our cases.

Treatment of DP was traditional with pimozide and some researchers have found good improvement with risperidone which was also seen in our cases.[2511] Shared psychotic disorder is seen in 5–15% of DP patients.[12] The psychotic disease is in only one patient (primary case), and he/she triggers symptoms in the other patient.[1314] Genetic factors, depression or dementia in the primary case and abnormal personality traits in the secondary case, disturbed interpersonal relationships may be predisposing factors. All the accompanying relatives of our patients had folie à deux.[3] The first line therapy for the folie à deux is the separation of the secondary case from the dominant case.[5] If the symptoms do not abate, antipsychotic drugs are needed.[5] However in our cases none of the relatives who shared the delusional belief agreed for any treatment or separation from the primary person. Hence, we just treated the patients and hoped for improvement in their relatives which was noted in our cases.

Consultation liaison by dermatologists and psychiatrists will definitely be useful for the diagnosis and treatment of these patients. As patients usually seek the opinion of the dermatologist first,[4] an early referral to the psychiatrist will not only prevent the associated psychiatric comorbidity but also the worsening of the skin condition.