Delusional parasitosis (DP) is a psychiatric disorder that presents with the belief that the body and/or intimate environment is infested with parasites. In primary DP, the delusions experienced are related solely to the parasitosis with no other signs of mental illness. In secondary DP, another disorder is the cause of the delusions, such as schizophrenia or schizoaffective disorder.1,2 We report a case of secondary DP successfully treated with quetiapine in our community mental health center.

A 57 year old Caucasian female with a history of schizoaffective disorder, bipolar type presented with multiple excoriations on her extremities. She stated that there were bugs and worms on her body, for which she was constantly scratching and tearing at her skin to get them out. The bugs were five-sided, legless “small black shrimp” with suckers and would “throw off” five eggs which would then spawn new sores. The worms were white and infested her back. Before coming to the clinic, she had been treated with mebendazole by a dermatologist and then “the sores started bursting open and [her] veins swelled up”.

When presenting to the clinic, the patient was being treated with quetiapine XR 200 mg daily for psychosis and mood stabilization. The decision was made to increase the quetiapine XR to 450 mg. Over the next 30 days, she showed some improvement, with the “outbreaks” occurring less often, but she was still reporting infestation as well as depression and anxiety. Her quetiapine XR dose was increased to 900 mg daily. Symptoms of DP were controlled for approximately 4 months, until she returned to the clinic reporting “an aquarium disease” along with “having snails and cooties”. Upon evaluation, the patient brought a jar containing dead skin cells, stating that she had captured some bugs to verify their existence. The dose of quetiapine XR was then increased to 1200 mg daily. One month later, the patient reported “being healed – the bugs were gone and the worms all died off”. She also no longer reported depression or psychosis related to her primary diagnosis. This dose was maintained, and for four months the patient endorsed no delusions or other psychotic symptoms. During her time with the clinic, she did not seek other forms of treatment through a dermatologist or by other means. Eventually, believing she no longer needed the medication, the patient self-terminated treatment and consequently was admitted to the local psychiatric hospital. It is unknown if she suffered a recurrence of her delusion.

Currently, there is no standard for treatment of DP.1 Only two placebo-controlled studies have been conducted, both utilizing pimozide in resolution and/or improvement of DP symptoms as their primary outcomes.1,2,3 Both studies were small double-blind studies, with only ten and eleven patients. They showed positive results with daily doses of two to eight milligrams of pimozide giving significant relief of itching symptoms and delusions.4,5 

Successful use of atypical antipsychotics has been reported in multiple case reports. These case studies report aripiprazole, risperidone, and olanzapine as successful treatments for primary DP or DP secondary to organic disease (vascular dementia, leucoencephalopathy).6,7,8,9,10,11 Also, case reports have been published utilizing quetiapine successfully, in low doses (50-300mg) and in combination with sertraline (150mg).3,12 To our knowledge, this report is the first published account of utilizing quetiapine to treat DP secondary to psychotic disorder.

Quetiapine is an atypical antipsychotic that has been used successfully in treating schizophrenia and bipolar disorder.13,14,15 The normal dose range is 150-800 mg daily, but it has been used at higher doses successfully.16,17,18 In this case report, quetiapine was used to treat DP with complete remission of delusions and subsequent success in treatment of schizoaffective disorder with no reports of adverse effects. This case supports the use of quetiapine in delusional parasitosis secondary to schizoaffective disorder.

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