The authors’ observations
During one of the clinical multidisciplinary treatment team meetings held for Ms. L, it was initially estimated that it would take at least 2 weeks for the delusional parasitosis to significantly respond to antipsychotic therapy. However, it is our professional opinion that the applied cognitive restructuring, with validation of her suffering, verbal support, and medication adherence counseling, expedited her recovery. This coincided with the aggressive titration of her antipsychotic and antidepressant, although the treatment team’s acknowledgment of Ms. L’s misery appeared to lower her guard and make her more susceptible to the power of cognitive restructuring. The efforts to validate the patient’s feelings and decrease hopelessness by telling her that the medication would make the bugs go away appeared to be the tipping point for her recovery. Patients with primary delusional parasitosis often are guarded and may feel alone in their predicament when they are met with perplexed responses from individuals with whom they discuss their symptoms. Compared with patients with schizophrenia, patients with delusional parasitosis maintain normal cognitive functioning, which may give them the insight to understand how their experience may be perceived as incompatible with reality.7 This understanding, coupled with some perceived helplessness, can lead a patient to fear having a severe mental decompensation, which can contribute to a delayed or complicated recovery.
The cognitive process described above might have been responsible for the difference in Ms. L’s MoCA scores because her performance in the initial test was hindered by her constant obsession with the bugs, which made her distracted during the test. By the time she responded to treatment, she gained significant clarity of thought, which enabled her to perform optimally in the test.
The difficulty in treating patients with delusional parasitosis may be further affected by lack of insight, and the fact that they often do not present to a psychiatrist for treatment in a timely manner because their delusion is impregnable and presents them with an alternate reality. These patients are more likely to seek out primary care physicians, dermatologists, infectious disease doctors, and entomologists because of the fervor of their delusion and the intensity of their discomfort. Because of this, a collaboration between these providers would likely lead to improved care and treatment acceptance for patients with delusional parasitosis.
Antipsychotics are the preferred medication for treating delusional parasitosis, and the literature supports their use for this purpose.6,8 The overall response rate is 60% to 100%.6 Previously, in small placebo-controlled trials, the first-generation antipsychotic (FGA) pimozide was considered first-line treatment for this disease.6 However, this antipsychotic is no longer favored because evidence is mounting that other FGAs result in comparable response rates with fewer tolerability issues.8,9
The bulk of data on the use of antipsychotics for treating delusional parasitosis comes from retrospective case reports and case series.6 Multiple antipsychotics have been shown to be effective in treating delusional parasitosis, including both FGAs and second-generation antipsychotics (SGAs).6,10 Published case reports and series have shown the effectiveness of the FGAs pimozide and haloperidol, among others. One review found that perphenazine, at doses up to 12 mg/d, resulted in partial remission for 2 patients and full remission for 1 patient.6
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