Managing Dermatologic Delusional Disorders: A US Psychodermatology Perspective for Clinicians

Abstract

Dermatological delusional disorders, such as delusional infestation (DI), are a unique type of psychosis in which the patient experiences specific delusions, such as parasites or inorganic materials that come out of their skin. Originally, this type of “encapsulated psychosis” was thought to be unresponsive to antipsychotic agents. However, over the past half a century, several medications with antipsychotic properties have been found to be effective in the treatment of these conditions in the USA, especially pimozide and risperidone. Despite effective treatments, several challenges may arise for clinicians in successfully treating patients with these conditions. These challenges include selecting an efficacious medication and skillfully practicing diplomacy and empathy while guiding patients toward effective management. Navigating interactions with patients with DI and their frequent denial of a psychiatric component to their condition often poses additional challenges to patient-provider rapport and proper and timely management. In the USA, many patients with DI are opposed to trying the conventional approach of psychiatric care and immediate trial of antipsychotic medications. This manuscript represents a single-center psychodermatology perspective on managing dermatologic delusional disorders. This article synthesizes clinical experience from a US clinic and situates that experience within the available evidence. High-quality comparative data are limited. Therefore, this paper highlights pragmatic engagement strategies, pharmacotherapy principles, essential safety monitoring, and research priorities. Experience-based recommendations are clearly labeled as such.

Key Points

Many patients with dermatologic delusional disorder in the USA decline psychiatric referral, creating a need for ethically defensible engagement in non-psychiatric clinics. Dermatologists should be equipped and prepared to effectively work with patients with DI despite the absence of a primary dermatologic etiology.

As per the experience in our US clinic, patient acceptance often improves once symptom relief is achieved, underscoring the importance of clear communication, support, and bias-free care.

Effective management requires a thorough workup, careful monitoring, and a constructive therapeutic alliance.

Rigorous scientific evidence for comparative pharmacotherapy in the treatment of DI is nearly nonexistent. Medications such as pimozide and risperidone may reduce symptoms, but treatment should follow individualized dosing and safety monitoring.

Introduction

There are unique types of psychosis that are almost exclusively seen in dermatology. These dermatological delusional disorders involve patients who believe they have “things” on or in their skin when there is no scientific or clinical evidence of the presence of such “things” [1].

Delusional infestation (DI), previously called “Delusions of Parasitosis,” is a rare condition affecting approximately 0.0002 to 0.03% of people, characterized by the belief that there are parasites in their skin despite the lack of evidence of such parasites [1, 2]. Medical discussions do not always lead to changes in the patient’s belief system. In fact, patients with DI can become frustrated, displeased, or upset when offered a logical conclusion from the objective findings from the examination and workup.

These conditions are often difficult to manage due to several factors, including cognitive dissonance between the workup and patients’ beliefs, as well as disagreement with treatment plans [1]. The real challenge in creating a workable management plan is not just about which medication is the most efficacious in treating their psychosis, but rather which medication is acceptable to the patient who does not believe they have a psychiatric-type condition. Moreover, an additional challenge is knowing how to navigate patient interactions and conversations, as being honest and truthful (“We found no evidence of parasites, you have psychosis and need to take an antipsychotic medication”) is likely to be upsetting to the patient, given the absence of insight inherent in some psychiatric conditions. This is compounded when patients are informed that the mainstay treatments are antipsychotics. Marked disagreement between clinical findings and the patient’s beliefs can create significant strain on the therapeutic relationship, potentially leading to escalation, such as complaints to the medical board or even malpractice suits. Many patients with DI refuse referrals to psychiatry and subsequently see only non-psychiatric physicians for their symptom workup and management.

Therefore, we present a step-by-step clinical strategy that is practiced in the University of California, San Francisco (UCSF) Psychodermatology clinic. The following recommendations are not meant to serve as a guideline nor a consensus, but rather practical recommendations intended to be useful to medical providers that are based on the authors’ experience of working with patients in the UCSF clinic with dermatological delusional disorders.

It is important to note that it is the dermatology provider’s choice whether to treat patients with DI based on their level of comfort with the condition and the management of antipsychotic medications. Should the provider decide not to be involved in the care of a patient with DI, it is fine to document the reasons and try to refer them to psychiatry. However, patients may be displeased at the mention of a psychiatric referral.

This is a practice-based perspective from a US-based clinic, the UCSF Psychodermatology clinic, and is not intended as a thorough, evidence-based review or guideline. This article synthesizes clinical experience with the available evidence to highlight the pragmatic implications and research needs for DI evaluation and management. The reader is recommended to use their judgment in deciding what part of this article is applicable to their practice. Moreover, if the patient agrees to be referred to a psychiatrist or other mental health professional, is accepting of the diagnosis of psychosis, and is willing to take medication despite it being an antipsychotic, then the authors agree that treatment by a mental health professional is preferred over treatment by a dermatologist. It is often the case in the USA that most patients with DI do not respond positively when managed using the standardized approach and recommended guidelines frequently utilized in other countries, such as the UK, where medications like amisulpride (not available in the USA), have been found to be the gold standard treatment of DI [3–5]. At the UCSF Psychodermatology clinic, there are many patients with DI who will only accept meaningful therapy when approached pragmatically. Therefore, this article is for patients who may benefit from a pragmatic approach, such as that illustrated here. The authors hope that the presented approach may give these patients a chance of recovery.

Clinical Approach to DI Management

Before the Clinic Visit

Preparation for clinic visits is essential in order to provide comprehensive and thorough care for patients with DI. As with every patient, each case should be approached with an open mind and any biases should be evaluated and addressed. In preparing for a patient with a suspected delusional disorder, it is important to be welcoming to begin building rapport from the start. Creating an atmosphere that feels calm and unhurried may support more effective patient engagement.

After the Patient-Provider Introduction

It can be very difficult to connect and build rapport with patients with true delusional disorders within the short timeframe of a 10-minute clinic visit. Providing undivided attention and creating a safe and open space for patients to talk, no matter how atypical their description may be, can assist in building rapport and creating a diagnostic and therapeutic plan. A thorough physical examination is essential not only for having an objective evaluation, but also to demonstrate that the patient’s concerns are being taken seriously. Creating a workup and treatment plan during this first visit is likely challenging given the limited time in the clinic. Rather, reframe your approach and view this visit as an initial opportunity to get to know and connect with your patient, building a strong rapport.

Sample provider response: Tell the patient that she/he has a very interesting and unique problem, and this is not the typical quick visit for more common conditions like acne or eczema. Offer to spend additional time with the patient beyond this visit. Inform the patient that their chief complaint deserves much more time than usual and ask them to return at a future date at the end of clinic so that more time can be spent with the patient. At UCSF Psychodermatology clinic, patients presenting with concerns of DI may need an hour-long appointment, which is communicated to the scheduling team and clinic staff. In summary, avoid placing yourself in a stressful and impossible situation in which you must evaluate and connect with the patient within the usual limited 5- to 10-min appointment time. In the management of a patient with delusions in dermatology, the most important visit is the initial encounter, when the patient either connects with the provider or fails to do so. With such patients, we typically let the front desk, medical assistants, and everyone else go home. If the senior provider has experience, is diplomatic, supportive, and non-confrontational with these patients, it is likely safe to interact with them without additional support. However, having support staff present during the initial meeting is completely up to the discretion of the clinician, based on their judgment and comfort level with managing patients with DI. Once the patient connects and trusts the provider, the subsequent visits are likely to be quicker and shorter than a typical dermatology follow-up visit.

After the Patient Returns

After a warm introduction, a thorough physical exam should be done to ensure that conditions like scabies incognito or bedbugs are not missed. Plan to do a thorough workup as follows [6], unless it has already been done recently:

1. Complete blood count.

2. Comprehensive metabolic panel (especially electrolytes in anticipation of using medications that may affect cardiac function, such as pimozide or other antipsychotic medications).

3. Thyroid function.

4. Vitamin B12.

5. Toxicology screening: care should be taken to use neutral, objective terminology to avoid stigmatization or unintended assumptions regarding substance use.

This workup will help to determine whether the patient has primary (spontaneous) or secondary delusions of parasitosis due to etiologies such as neurologic conditions, multiple sclerosis, and substance use [6]. Secondary cases of DI will require treatment of the underlying cause, which often necessitates a referral and coordination of appropriate care.

The following discussion pertains to primary (i.e., spontaneous) cases of DI.

Assessment of Primary DI

Once it is established that patients are experiencing primary DI, it is important to evaluate their degree of delusionality as this helps the provider to determine how to best communicate with and make therapeutic recommendations for the patients. While the prognosis of symptom severity is highly variable, disease duration is typically chronic, and without treatment, patients often demonstrate a progression in self-destructive behaviors [7]. Less severe presentations of DI are characterized by feelings of abnormal sensations without delusions. Patients with milder symptoms may also begin to worry about parasites but admit that this may sound irrational. It is important to build and maintain rapport while communicating with patients. In milder cases, as illustrated above, providers are likely to be able to safely engage in a typical, two-way conversation [8]. More severe presentations of DI are characterized by intense worries about parasites. In our clinical experience, if it becomes clear that the patient is more severely affected and is experiencing true delusions, whereby they cannot tolerate any explanation other than their own, it is essential to prioritize safety. Care should be taken to avoid upsetting the patient.

Treatment Strategy for Delusional Infestation

All providers should be familiar with the necessary close supervision, labs, and clinical testing, such as an EKG (pre-treatment, during treatment, and after treatment) and perhaps even the Abnormal Involuntary Movement Scale (AIMS) testing for monitoring of anti-psychotic medication side effects, prior to prescribing [9]. Once the negative workup is discussed and patients are informed that no parasites, fibers, or other materials were found, the next appropriate step is to skillfully introduce antipsychotic medications in such a way to maximize the patient’s acceptance of the treatment.

A Pragmatic Trial-and-Error

In our clinical experience, many patients do not respond to the initial suggestion of treatment with an antipsychotic for their psychiatric illness. Avoid presenting the medication options in an overly simplistic manner, as this may cause the patient to dismiss them outright. Acknowledging that the patient’s symptoms may have a substantial impact on their daily life may support a constructive therapeutic dialogue that includes discussion of pharmacologic therapy that could relieve or even cure their symptoms. If the patient is willing to try these medications on a “trial-and-error” basis, then the provider may proceed to prescribe them after a thorough review of their medical history and risk factors.

In our clinical experience at UCSF, pimozide is often the most favorable and acceptable treatment for patients who are reluctant to consider medications with psychiatric indications. Providers may find it helpful to inform the patient that pimozide is a first-generation antipsychotic, although it has no psychiatric indications in the USA. According to the US FDA, the only indication is for Tourette’s syndrome, but it is often used off-label for multiple conditions, including DI [10]. Many medications with chemical structures similar to antipsychotics (such as some antiemetic or antihistamine agents), are not considered to be antipsychotics because they have no such FDA indications or use in psychiatry. From the authors’ experience, pimozide is often the only option for treatment that is acceptable to dermatological patients with delusions who are strongly against the idea that there is some psychiatric involvement in their condition.

If patients are open to trying risperidone, a second-generation antipsychotic, despite its FDA psychiatric indication, treatment may be presented as a “trial-and-error” method in which patients start at a low dose of pimozide or risperidone and incrementally increase the dose. In older adults, clinicians must exercise caution given the increased risks that antipsychotic medications carry in patients with dementia-related psychosis and other comorbidities. Treatment choice should be individualized and guided by safety considerations, such as age, co-administered medications, and cardiovascular, renal, or hepatic disease or risk factors.

Pimozide: Data, Considerations, and Dosage

Data

In the USA, pimozide has long been an off-label treatment for DI. In addition to clinical expert experience, efficacy of pimozide in the treatment of DI has been seen in case series/reports, which have shown that a daily dose of 1 to 5 mg led to an improvement in or full remission of symptoms in 61% of cases [11]. Additionally, onset of symptom improvement was seen within 3 to 4 weeks in those who responded to the medication [11]. A double-blind, placebo-controlled crossover trial of 11 patients with DI treated with 1 to 5 mg of pimozide or placebo for 6 weeks separated by a 4-week washout period, found that pimozide was significantly better than placebo in relieving itch delusions [12]. However, no difference was found between pimozide and placebo for feelings of vermin or excoriation [12].

At the UCSF Psychodermatology clinic, pimozide has been used as the first-line treatment for patients with DI, with improvement or complete resolution in symptoms in most patients. While current scientific data are limited by small sample sizes or poor methodology description, this serves as a promising area of future research.

Considerations

Given the potential side effects of pimozide, close monitoring for neurologic symptoms and cardiotoxicity should be incorporated into care.

• Neurologic risks: Providers should monitor for extrapyramidal movement disorder symptoms, such as Parkinsonism, akathisia, dystonia, and tremor. While rare, providers should also be vigilant of serious conditions, such as neuroleptic malignant syndrome and tardive dyskinesia [13–15].

• Cardiotoxicity: All patients should be monitored with an electrocardiogram at baseline and during periodic follow-up, depending on their risk factors and dosage. Cardiotoxicity is a concern at higher doses and may be less concerning for patients who take less than 10 mg/day, are not elderly, and have no history of cardiac arrhythmia [1, 16].

• Specific populations: Because some patients are slow metabolizers of pimozide, the FDA recommends that, if any patient is to be treated with more than 4 mg of pimozide/day, CYP2D6 enzyme testing must be performed [17].

Monitoring should be assessed at baseline and at regular intervals based on the patient, risk factors, and clinical response.

Pimozide Dosage

Given the lack of evidence on an appropriate starting and maintenance dose, the following recommendations are based on clinical experience at the UCSF Psychodermatology clinic. Medication management should be individualized and closely monitored by the provider.

At the UCSF Psychodermatology clinic, pimozide is started at 0.5 mg or 1 mg and increased by 0.5 mg every 2–3 weeks until 3–4 mg/day is reached. Authors’ experience has seen most DI patients respond well to a dose of 3–4 mg/day, but occasionally patients require a higher dose. Likewise, some patients with DI respond well to a lower dose.

Risperidone: Data, Considerations, and Dosage

Data

Risperidone has been used to treat DI since 1995 and is widely used as an efficacious treatment option. Rigorous controlled trial data are limited, but data from a recent systematic review evaluating 51 relevant articles have reported a favorable response to risperidone in treating DI [18]. A case series by Guedes et al involving 27 patients similarly found that risperidone effectively controlled symptoms in most patients. In this study, the starting dose ranged from 1 mg every other day to 1 mg daily, while the maintenance dose ranged from 1 mg three times a week to 8 mg daily. Of note, four patients had a dose reduction due to side effects, and three patients were switched to another antipsychotic despite good response. Only one patient in the study did not respond to risperidone [19].

Considerations

Given the potential side effects of risperidone, close monitoring for metabolic changes and neurologic symptoms, management of cardiovascular risks, and dose adjustments in specific populations should be considered [20].

• Metabolic monitoring: Risperidone is associated with hyperglycemia, dyslipidemia, and weight gain, which can increase cardiovascular risk and risk for metabolic syndrome. Providers should monitor glucose regularly in patients with diabetes or with an elevated risk for diabetes. Weight gain and lipid profiles should be regularly monitored.

• Neurologic risks: Providers should monitor for extrapyramidal movement disorder symptoms, such as Parkinsonism, akathisia, dystonia, and tremor. While rare, providers should also be vigilant for serious conditions, such as neuroleptic malignant syndrome and tardive dyskinesia.

• Cardiovascular precautions: Particularly at risperidone initiation, re-initiation, or dose increase, providers should screen for orthostatic hypotension and syncope by monitoring blood pressure and reviewing side effects at each visit.

• Specific populations: Patients with severe renal or hepatic impairment should be started on a lower daily dose. When risperidone is co-administered with CYP2D6 inhibitors or inducers, dosage may need to be reduced or increased, respectively.

Monitoring should be assessed at baseline and at regular intervals based on the patient, risk factors, and clinical response.

Cytochrome P450 2D6 (CYP2D6) also metabolizes risperidone; however, there is no recommended threshold of dosage that calls for CYP2D6 enzyme testing [21]. The package insert acknowledges that CYP2D6 slow metabolizers may be at risk of higher risperidone blood levels, as CYP2D6 metabolizes it to its inactive form. The 2017 Summary of Recommendations from the Dutch Pharmacogenetics Working Group of the Royal Dutch Association for the Advancement of Pharmacy, advises that no action is needed for CYP2D6 poor, intermediate, or ultrarapid metabolizers [21]. However, careful dose escalation should always be practiced in patients who are slow metabolizers.

Risperidone Dosage

Given the lack of evidence regarding appropriate starting and maintenance doses, the following recommendations are based on clinical experience at the UCSF Psychodermatology clinic. Medication management should be individualized and closely monitored by the provider.

At the UCSF Psychodermatology clinic, the dosage of risperidone is managed similar to pimozide in that starting slow and low at the lowest effective dosage for the shortest duration possible can minimize risk of adverse side effects, many of which are dose-dependent [20, 22]. Risperidone is started at 0.5 mg or 1 mg and increased by 0.5 mg every 2–3 weeks until 3–4 mg/day is reached. Even though the authors’ experience has been that most patients with DI respond well to a dose of 3–4 mg/day, there are occasional patients who require a higher dose or may respond well to a lower dose.

For both pimozide and risperidone, expectation setting is essential when starting therapy. In the authors’ experience, patients may not experience symptom improvement until they reach a 3-mg daily dose, and the slow incremental increase is intended to prioritize their safety. Additionally, most patients experience a dramatic decrease in their symptoms and often report that the medication is killing their parasites or stopping the formation of materials in their skin.

Medication Maintenance and Taper

The following describes the clinical approach at the UCSF Psychodermatology clinic. Clinicians should always individualize a treatment plan based on the patient’s symptoms, side effects, and risk of recurrence.”

Patients should be followed closely as they are titrated up on these medications, as displayed in Fig. 1. Once they reach a dose that effectively treats their symptoms to near or full resolution, it is advised to continue that dose, even if it is lower or higher than 3 mg daily. Once they reach this state of complete or near complete elimination of symptoms, continue this dose for an additional 3–4 months to avoid the risk of recurrence by decreasing the medication too soon. If no recurrence occurs for an additional 3–4 months from their initial resolution, their medication can be gradually tapered down. The authors advise never to abruptly stop pimozide, risperidone, or other agents unless absolutely necessary due to side effects. Tapering dose should not exceed a 0.5-mg decrease per month [23].

Fig. 1.

“Trapezoid” approach to dosing pimozide and risperidone for dermatological delusional disorders. A The same dosages can be used for pimozide and risperidone. Start with 0.5–1 mg/day. Explain that dosing will be gradually increased for safety. Inform the patient not to expect benefits until a typical dose of 3 mg daily is reached. Expectation management is essential to prevent premature discontinuation. B If tolerated, increase the dose by no more than 0.5 mg every 2–4 weeks until the patient reports significant improvement in their symptoms. Apart from the decrease in formication (crawling, biting, stinging, burrowing sensation), the patient typically also experiences a significant decrease in mental preoccupation regarding the delusional ideation. C Once the patient experiences treatment efficacy, continue on that dose (even if that is less than 3 mg/day) since maximum improvement is often not seen for at least 4–6 weeks at any given dose. If the patient is not experiencing adequate response, even if the dose is now 3–4 mg/day, the dose can be further increased incrementally as above, but beyond 4 mg/day, for pimozide, testing for CYP2D6 is required to ensure that the patient is not a slow-metabolizer of pimozide. D Once symptoms resolve completely, continue this dose for an additional 3–4 months. E After this period without symptom recurrence, begin with a slow taper. Ensure that the dose is not abruptly cut, as symptoms may recur, which can be extremely discouraging to the patient. In fact, it is not unusual for the patient to become emotionally attached to the medication and be reluctant to discontinue it. Therefore, the tapering typically happens very slowly. F Continue a slow, gradual taper of no more than 0.5 mg (half a tablet) every 4 weeks, and therefore, it may take as much as 6 months before the patient is off the medication and is symptom-free. G Patient achieves resolution of their symptoms while off medication

Patients should be informed that the ultimate goal is to be medication-free with no symptoms. In the authors’ clinical experience, many patients are able to accomplish this. Many patients who show improvement or resolution of symptoms often do not mind long-term administration of the medication and may even be hesitant to decrease their dosage. In this case, patients can be reassured that the taper will be slow, and that together you’ll work to ensure the symptoms do not return.

Additional Considerations for Psychopharmacologic Therapies

Mainstay treatments for DI include pimozide, risperidone, olanzapine, and aripiprazole. All have side effects that are important to consider, such as extrapyramidal symptoms. Tardive dyskinesia from pimozide is extremely rare with the doses and durations used to treat DI, with only two cases documented in the medical literature after half a century of pimozide use in dermatology [15, 24].

Medications should be carefully administered, using a trapezoid strategy in which the medication is used in a time-limited fashion. Like a trapezoid, the dose of the medication is gradually titrated up, then maintained for a while until symptoms disappear. The dose can then be held for an additional 3–4 months before slowly tapering off the medication [7]. This approach likely explains why tardive dyskinesia is extremely rare.

Based on experience at the UCSF Psychodermatology clinic, most patients with DI respond to antipsychotic medication. However, what happens when multiple antipsychotic agents fail and the patient now wants antiparasitic or other antipathogen treatment? According to the authors, in such cases it must be explained to the patient that the UCSF Psychodermatology clinicians are not a parasitologists, infectious disease specialists, or entomologists and that the patient should seek the help of those other specialists once it becomes clear that the “trial-and-error” approach has failed. The authors have not encountered cases where a DI patient has shown no response at all despite a good trial of multiple antipsychotic agents.

Conclusion

In summary, dermatology has its own unique subset of psychotic conditions, such as DI. It is fortunate that there are pharmacologic therapies known to be effective in treating DI patients that have the potential to cure their condition. However, the real challenge is often obtaining patient cooperation for initiating these medications, given the hesitation that exists around the fact that FDA psychiatric indications are present in all antipsychotics except pimozide. It is important to form and maintain an effective therapeutic alliance with patients.

1. Build a strong rapport, which should take precedence over discussions of pharmacologic therapy.

2. Skillfully broach the subject of pharmacotherapy only after a strong rapport has been built.

3. Employ the trapezoid strategy of treatment, which may lead to a cure of their symptoms while minimizing the risk of tardive dyskinesia.

In the authors’ clinical experience, these conditions are eminently treatable. However, there are often delays in the time it takes to receive proper care and referral, mainly because patients do not want to see mental health or psychiatric professionals, and most dermatologists are hesitant to use medications like pimozide and antipsychotics. By recognizing the unique challenges, a clinician can approach patients with empathy and skillful communication strategies to build trust and rapport, and guide them toward an effective and lasting improvement or cure of their symptoms.

Funding

None.

Declarations

Conflict of interest

Dr. Andrea Leung has no disclosures. Dr. John Koo is a consultant for Regeneron-Sanofi, Castle, Pfizer, Arcutis, and Celltrion. He is also a speaker of Abbvie, Regeneron-Sanofi, Pfizer, SUN, Leo, Dermavant, Eli Lilly, Bristol-Meyer-Squibb, Galderma, UCB, and Pfizer. However, because the topic of this article is psychodermatology and not psoriasis or eczema, none of these companies are relevant for the research, authorship, and/or publication of this article.

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Author contributions

AL contributed to conceptual development, literature review, manuscript preparation, and manuscript revision. JK contributed to conceptual development, manuscript preparation, manuscript revision, and project supervision. Both authors read and approved the final version.