A case of delusional parasitosis presented as shared psychotic disorder treated successfully with aripiprazole

Sir,

Delusional parasitosis is a rare psychiatric disorder characterized by the unshakable and false belief of being infested with small organisms, insects, or parasites without any medical evidence.[1] It has been described as acarophobia, parasitophobic neurodermatitis, and Ekbom syndrome and named as “delusional parasitosis” by Wilson and Miller in 1946.[2] Approximately 5%–15% of patients, delusional infestations are shared with other people such as close relatives, partners, and family members and presented as shared psychotic disorder.[3] We report two cases with delusional parasitosis meeting the diagnostic criteria of shared psychosis and successfully treatment of disease with aripiprazole, a well-tolerated atypical antipsychotic.

A 66-year-old Turkish graduated from primary school and married male was referred from the dermatology department with an 8-month history of feeling of insects crawling across his skin and itching on his all body, especially on both the legs. In the detailed dermatological examination of the dermatology clinic, no evidence of parasitic infestation was found, and he was treated for itching, but he was referred to the psychiatry department because of no regression in his complaints. He had taken shower numerous times a day, used too much soap, sprayed the house, and threw away his clothes to get rid of the insects. He told that he put the insects in a box that he saw on his bed and sent them to a laboratory to determine what they were. However, he was informed as there were no insects or parasites. On psychiatric examination, he was anxious and depressive. In his thought content, he had the delusion as his body was invaded by insects. The patient brought a small box along with him. He said that he put the insects which he had found in his bed into this box. Only blanket wool was seen in the box. Mini-mental test score was 27/30. Hamilton Depression Scale score was 11. Hamilton Anxiety Scale score was 11. In his medical history; he has been receiving drug therapy for ischemic heart disease and hypothyroidism. His neurological examination was normal. Routine biochemistry, blood count, and hormone test results were normal except for a height of 5.86 U/mL (0.27–4.2 ul U/mL) in thyroid-stimulating hormone (TSH) levels. In brain magnetic resonance imaging (MRI), no pathology was revealed except age-matched changes.

The patient's wife also presented to the dermatology department along with him for itching complaint. They have been living together for 45 years. She was a 66-year-old woman and graduated from primary school. She also told that she had itching and had been contaminated by the insects for 6 months. Her complaints have started after 2 months of her husbands' complaints. She told that she had needed to take shower numerously, ventilated the house and household items, and cleaned the house constantly. On her psychiatric examination, she was anxious and depressive. She had delusions in her thought content that she was contaminated by the insects and insects had been infested on her body. Mini-mental test score was 27/30. Hamilton Depression Scale score was 14. Hamilton Anxiety Scale score was 17. She has been receiving drug therapy for essential hypertension and hypothyroidism. Neurological examination was normal. Routine biochemistry, blood count, and hormone tests were low in free T4: 0.827 ng/dL (0.93–1.7 ng/dL) and high in TSH: 12.9 μlU/mL. In brain MRI, there was no pathology except age and hypertension secondary changes.

According to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition diagnostic criteria, we diagnosed shared psychotic disorder and delusional disorder (somatic type).

The patient was started on 5 mg/day of aripiprazole, and the dose was increased gradually to 10 mg/day. He tolerated well. There was complete remission of the patient's delusion at 8 weeks of treatment. On following examinations, he did not develop the delusion again. For the shared psychotic disorder, we advised the husband and wife to live separately. Furthermore, the wife was started on 10 mg of escitalopram and increased to 15 mg/day during control examinations. Her anxiety and depressive symptoms were significantly regressed. She also did not mention about insects in the control visits.

Only with separation and aripiprazole treatment led to the improvement in the husband's and wife's psychotic symptoms.

There are several case reports about the use of atypical antipsychotics in the treatment of delusional parasitosis.[4,5,6] Aripiprazole, which is also an atypical antipsychotic, has a different pharmacological profile from other atypical antipsychotics and is a well-tolerated drug. It has been reported that it may cause a decrease in depression and anxiety symptoms that can be seen in patients with delusional parasitosis because of its 5 hydroxytryptamine 1A partial agonism.[7] Therefore, aripiprazole may be the cause of choice in patients with delusional parasitosis, especially in the elderly, having cardiac problems, and accompanied by depression and anxiety.

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Conflicts of interest

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