Delusional infestation in dermatology in the UK: prevalence, treatment strategies, and feasibility of a randomized controlled trial

Background. Delusional infestation (DI) is considered rare, but true epidemiological studies are only available for Germany. Patients usually contact dermatologists, and psychiatric referral is often impossible. Aim. To estimate the prevalence of DI in UK dermatology clinics, to examine the feasibility of a multicentre randomized controlled trial (RCT) in dermatology, and to evaluate the psychopharmacotherapy of DI in dermatology. Methods. A short questionnaire survey was distributed to 231 UK dermatologists, asking how many new and ongoing patients with DI they had seen in the past 3 years, which treatments they had used, and whether they thought an RCT would be feasible. Results. The return rate was good (44.6%, n = 103 of 231). In total, 103 British dermatology consultants reported 182 cases seen over the past 3 years and 54 current cases. The 3-year prevalence of DI in dermatology outpatients was 4.99 per million; the point prevalence was 1.48 per million. Around a third (35%) of patients were prescribed psychotropic medication, mostly pimozide. Respondents were evenly split in their view of the feasibility of organizing an RCT of treatment of DI. Conclusions. Our survey covers more than half of the UK population, allowing the first estimate of basic epidemiological data on DI in dermatology in the UK. Our prevalence estimates indicate that DI is not as rare an illness in dermatological practice as previously assumed. There are potential difficulties in organizing an RCT of DI treatment. British dermatologists do not regularly use second-generation antipsychotics as their first choice of treatment.