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Ethan C. Levin, MD,* and Uwe Gieler, MD† The most common monosymptomatic hypochondriacal psychosis encountered by a der-matologist is delusions of parasitosis. In this condition, patients have an “encapsulated”fixed, false belief that they are infested with parasites or have foreign objects extruding fromtheir skin. The patient will often experience feelings of biting, crawling and stinging relatedto the delusion. Most patients do not have other major psychiatric problems outside of theirencapsulated delusion. The patient usually presents with a long history of symptoms andmultiple visits to physicians in more than one specialty. Without an informed approach tothese patients that focuses on the development of therapeutic alliance, clinical interactionscan become very unpleasant. However, when treated with pimozide, risperidone, or otherantipsychotic medications, patients have a very high response rate. Therefore, it is impor-tant for dermatologists to be able to handle these cases and know that the development ofthe therapeutic alliance is the key step to successful management.
Semin Cutan Med Surg 32:73-77 2013 Frontline Medical Communications KEYWORDS psychodermatology, delusion, parasitosis, infestation, morgellons
FirstdescribedbyThibiergein1894,delusionsofparasi- schizophrenia, which is a multifunctional deficit involving tosis is a psychiatric condition characterized by a fixed, more than just delusional ideation. In addition, patients with false belief that one is infested with parasites and is often schizophrenia have visual or auditory hallucinations as well accompanied by hallucinatory experiences compatible with as deterioration in social, occupational, and personal func- this For example, patients frequently complain of tion as shown by a “flat” or “inappropriate” affect. This is in formication, which are feelings of biting, crawling, and sting- contrast to MHP, where delusions are typically “encapsu- ing under the The delusion is often “encapsulated” lated”, and the patient generally does not have any other meaning the patients are otherwise fully functional. Although major psychological disturbance. Delusions of parasitosis is rare, delusions of parasitosis is important for dermatologists the most common MHP, however there are other types of to understand. Without an informed approach to these pa- encapsulated delusional disorders that are seen by dermatol- tients, clinical interactions can become very unpleasant.
ogists including delusions of bromosis and delusions of dys- However, when treated with the appropriate antipsychotic medication, patients have a very high response rate.
In delusions of bromosis, patients are convinced they emit Delusions of parasitosis is a type of monosymptomatic offensive odors and think this is why others avoid hypochondriacal psychosis (MHP). MHP is characterized by However, those around the patient do not smell anything a monosymptomatic delusional ideation focused on a single bad. Delusions of dysmorphosis refers to the belief that one is concern that the patient perceives to be the cause of a serious physically misshapen and unattractive, oftentimes involving medical It is important to distinguish MHP from a specific facial feature or small part of the This delu-sion represents the extreme end of the spectrum of bodydysmorphic disorder.
*Department of Dermatology, University of California, San Francisco.
Historically, these 3 types of MHP were described as “pho- †Clinic of Psychosomatic Medicine and Psychotherapy, Justus-Liebig-Uni- bias”, as in parasitophobia, bromophobia or However, these conditions are now more appropriately clas- Disclosures: The authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr Gieler has received grants sified as delusional Patients with phobias usually from the German Government for scientific research as well as grants for have some insight that their fear is irrational or extraordinary clinical studies belonging to acne, atopic dermatitis, and alopecia. Dr whereas patients with MHP do not have any insight that their Correspondence: Ethan C. Levin, MD, Department of Dermatology, Univer- Delusions of parasitosis can be classified into 2 different sity of California, 515 Spruce Street, San Francisco, CA 94118. E-mail: categories, primary and secondary. Primary delusions of 1085-5629/13/$-see front matter 2013 Frontline Medical Communications E.C. Levin and U. Gieler
parasitosis is an idiopathic disorder that meets the Interna- parasitosis is unknown. However, one study shows an asso- tional Classification of Diseases 10th revision criteria for per- ciation between secondary delusions of parasitosis and brain sistent delusional disorder and the Diagnostic and Statistical lesions located in the In this retrospective study, Manual of Mental Disorders, revision IV for delusional disor- of the 8 patients with secondary delusions of parasitosis (ex- der, somatic Secondary delusions of parasitosis, or cept for those with another psychiatric disorder), 8 had mac- conditions that mimic delusions of parasitosis, arise from roscopic brain lesions as seen on cranial magnetic resonance another medical condition affecting the central nervous sys- imaging or computed tomography imaging. The lesions were tem. These conditions include cerebrovascular accidents, most commonly found in the putamen of the basal ganglia.
cardiovascular disease, B12 deficiency, diabetes, schizophre- The investigators did not see any brain lesions in the other 9 nia, depression and Toxic ingestion of substances patients, 5 of which had primary delusions of parasitosis and such as cocaine and amphetamines can also lead to secondary 4 who had secondary delusions of parasitosis from another delusions of parasitosis. Conditions that mimic delusions of parasitosis usually are not treated with antipsychotics.
Rather, the underlying cause is treated.
Clinical PresentationThe clinical presentation of delusions of parasitosis com- Epidemiology
monly includes a long history of symptoms with multiplevisits to physicians in more than one In many Even though delusions of parasitosis is the most common cases, the patient will have made an attempt at getting rid of MHP encountered by dermatologists, the overall prevalence the parasites with antiparasitic agents, hiring exterminators, of the disorder is low. In a study by Pearson et al that sur- or even moving to a different Oftentimes the infes- veyed Northern California residents, the prevalence of delu- tation is blamed on a particular inciting life event.
sions of parasitosis was reported as 3.65 cases per 100,000 It is common for patients to present with evidence of the perceived infestation in the form of hair, garment fibers or Although delusions of parasitosis is infrequently encoun- pieces of skin stored in small bags or containers (known as tered, it does tend to affect specific age groups. The average the “ziplock” sign or in the past, the “matchbox” The age of onset is in the 5th or 6th decade of life and is at least patients’ delusions are usually narrow in focus, as on a par- twice as common in women than in These patients ticular parasite, but can be fixated on other objects. For ex- tend to be from higher socioeconomic classes. Delusions of ample, Morgellon’s disease is a type of delusions of parasito- parasitosis can also affect young patients and the number of sis often involving fibers extruding from the skin and orifices men and women are equally affected in this population. The of Morgellon’s is a lay term that is widely used by younger patients are often from lower socioeconomic classes patients, but has never been officially defined or accepted by and have increased likelihood of substance People that cohabit with someone with delusions of para- The skin findings in delusions of parastitosis can range sitosis can share the same delusion. This is known as “folie a from normal-appearing skin to excoriation, lichenification, deux” and occurs in 5%-15% of cases. The person who first prurigo nodularis, erosions or ulceration. Any positive find- develops the delusion is known as the inducer and persuades ings are self-induced from the patients’ attempts to dig out others in the household to share in the delusional belief.
Treatment of the inducer usually results in the spontaneousrecovery of the other affected The differential diagnosis for delusions of parasitosis spansboth dermatologic and psychiatric conditions. It is important There are 2 hypotheses to explain the development of delu- to first rule out a true primary skin For example, difficult-to-diagnose scabies or transient acantholytic derma-tosis (Grover’s) can be mistakenly diagnosed as delusions of The patient has a hallucinatory perception, such as abiting or stinging feeling, which leads to a fixed false parasitosis. In these cases, the primary lesion can be hidden belief about the origin of the perception (ie, from in- by excoriations. Therefore, a careful physical exam should always be performed to search for any nonexcoriated, pri-mary lesions suitable for biopsy.
The patient is primarily delusional, which causes thepatient to perceive feelings associated with the delu- Cutaneous dysesthesia is one of the most common diagnoses sion. For example, the patient believes that he or she is in patients initially suspected to have delusions of infested with insects and as a result perceives feelings of Cutaneous dysethesia usually manifests as formication, which is a sensation of biting, crawling, or stinging that can occur in theabsence of delusions of infestation. Most cases of formication are Secondary delusions of parasitosis arise from another medi- primary and idiopathic. Rarely, the sensations are secondary to cal condition that affects the central nervous system, such as a cerebrovascular accident or diabetes. How the primary dis- If untreated, some patients with formication may gradually ease process actually leads to the development of delusions of come to believe that their symptoms are due to an infestation.
Delusions of parasitosis
In the authors’ opinion, it is critical to treat these patients nology as the patient, many of which will refer to their disease with an appropriate antipsychotic agent as soon as possible to as Morgellon’s. Using this term is your discussion with the prevent the progression to delusional ideation. In order to be truly delusional, one must have a fixed belief that there is an Once in the room, maintain control with a structured in- infestation. Pimozide or risperidone is usually successful in teraction. Do not confront the patient’s delusion as a primar- treating formication even if the patient is not delusional.
ily psychiatric disorder as this can lead to an unpleasant Other patients experience formication as a result of sub- interaction that may become a barrier to treatment. The pa- stance abuse, especially with amphetamines or cocaine.
tient may get defensive and think his or her skin condition is These substances can produce symptoms identical to those being brushed aside as a psychological problem.
seen in delusions of parasitosis. In fact, formication is a well- It is equally important to avoid confirming the patient’s known side effect among drug users and is colloquially re- delusion. The more support the patient’s delusion has, the ferred to as “cocaine Among patients who experience more fixed it becomes. By asking targeted questions, deter- these symptoms, relief only occurs upon cessation of the mine whether the patient’s primary concern is to convince others about his or her delusional beliefs or to no longer have Another differential diagnoses for delusions of parasitosis symptoms of formication. Patients who are most focused on is any condition that mimics delusions of parasitosis (“sec- symptom relief are oftentimes open to therapy. In contrast, ondary delusions of For example, the delu- patients who are most interested in convincing others about sion may be a manifestation of paranoia in a schizophrenic the validity of their delusion are usually not open to therapy patient. Other conditions that can mimic delusions of paras- other than that which clearly kills an organism. Either way, itosis include B12 deficiency or abnormal thyroid function.
these patients usually require many visits to establish thera- In all of the above cases, treatment is determined by the peutic rapport before medication can be discussed. There- fore, the physician should not feel pressured to talk about The clinician must use his or her best clinical judgment to determine whether the patient is truly delusional. True delu-sions represent the extreme in a spectrum of thought pattern, which also includes normal ideation, overvalued ideas, and Address the patient’s complaint seriously and perform a thor- delusional ideation. Patients with overvalued ideas overem- ough physical exam. Pay attention to whatever “specimens” are phasize one particular viewpoint but have the ability to con- brought in by the patient. If this proves too cumbersome be- sider others. Patients with delusional ideation are fixed in cause of the messiness of the “specimen” brought in by the their beliefs, however may have minimal insight that other patient, provide the patient with some glass slides to take home.
perspectives exist. Anything less than a truly delusional pa- Instruct the patient to put clear plastic tape over the speci- tient can be counseled and reassured with rational evidence mens (not the usual matted Scotch tape) on the slide and such as a negative skin exam, culture, or microscopic bring them to the next visit. Most frequently, pieces of skin, However, this evidence will not be enough to satisfy a truly fibers or hair are brought in. The glass slide technique is a delusional patient, where antipsychotic therapy is often re- time-efficient and hygienic way to address the patient’s con- cern. After examining the specimens, discuss the results withthe patient without confirming the delusion. Once the pa- Management
tients believe the clinician agrees with them, they becomeincreasingly difficult to treat. Finally, offer to return the spec- We break down the approach to complex patients with de- imen to the patient. Some patients are very emotionally in- lusions of parasitosis into the following simple steps: vested in the specimen they have collected.
In addition to bringing in a specimen as proof their infes- tation, some patients may request a skin biopsy of one of their perform a thorough history and physical exam, and lesions. This can be performed at the discretion of the phy- provide initiation and maintenance pharmacologic sician, especially to build rapport with the patient and to avoid a power struggle which may endanger rapport.
Therapy should only be considered once secondary causes of When clinical suspicion warrants, consider performing delusions of parasitosis have been ruled out.
laboratory tests to rule out some of the secondary causes ofdelusions of Some of these tests include: com- plete blood count (CBC) with differential, serum electrolytes,liver function tests, thyroid function tests, serum calcium, The first step in establishing therapeutic alliance is to have a blood glucose, serum creatinine, Vitamin B12, folate, urinal- positive mindset, and to be prepared for a negative, defensive ysis, urine toxicology, HIV and Raid Plasma Reagin.
and paranoid patient that has visited numerous doctors, triednumerous treatments unsuccessfully, and is skeptical of themedical One effective tactic is to treat the pa- tient like a “VIP” and let them know they are special patients Traditionally, the treatment of choice for delusions of paras- requiring extra time. Another strategy is to use similar termi- itosis is pimozide This medication is a centrally E.C. Levin and U. Gieler
acting dopamine antagonist that primarily blocks D2 and therapy is 5 to 6 If delusions recur, pimozide can 5HT2 Other antipsychotics, including risperi- be restarted and titrated as above to control the episode.
done (Risperdal) and olanzapine (Zyprexa), are becoming Treating on an episodic basis in patients with recurrent dis- increasingly more popular in treating delusions of parasitosis ease is preferred. This is done to limit the incidence of tardive due to similar efficacy and more favorable side effect pro- dyskinesia, which is a rare side effect associated with long- However, in the United States, pimozide is unique term use of low-dose typical antipsychotics. Tardive dyski- because it does not have an Food and Drug Administration nesia is characterized by repetitive, involuntary, and pur- (FDA) indication for the treatment of a psychiatric disorder; poseless movements such as lip smacking, lip puckering, or the only FDA indication is in the treatment of Tourette’s tongue protrusion. Rarely, some patients develop involun- syndrome. As a result, patients are more accepting of this tary movements of the mouth after tapering off pimozide.
medication since it is not typically prescribed as an antipsy- These movements are known as withdrawal dyskinesia, and chotic. In addition, the only randomized trials investigating are distinguished from tardive dyskinesia in that they are the treatment of delusions of parasitosis used time Tardive dyskinesia from pimozide use in delu- Pharmacologic therapy can be discussed once adequate sions of parasitosis has not been reliably described in medical therapeutic rapport has been developed. A pragmatic ap- proach is to present pimozide as “trial and error” treatment In addition to the risk of side effects, Pimozide also has the which is very effective at decreasing or eliminating the pa- risk of drug-drug interactions. These interactions are thought tient’s mysterious condition of unknown This ap- to be related to medications that affect cytochrome P450 proach avoids discussion of the medication as an antipsy- As a result, the FDA has listed the following medica- chotic which can cause most delusional patients to reject the tions as contraindicated due increased risk for prolonged QT treatment. As stated earlier, pimozide has no psychiatric in- interval: macrolide antimicrobials (ie, azithromycin, erythro- dication in the United States; the official FDA indication is mycin), azole antifungals, protease inhibitors, and Tourette’s syndrome. It can be helpful to explain to patients Grapefruit juice is also an inhibitor of cytochrome P450 3A that they are not being treated for this condition.
and should be avoided when taking pimozide.
When starting pimozide, the medication should be care- Other possible therapies for delusions of parasitosis in- fully titrated to reach a therapeutic response. Begin the pa- clude second generation antipsychotics like risperidone tient at 1 mg daily, increasing by 1 mg increments every 2 or (Risperdal) and olanzapine Risperidone, like 3 weeks until optimal clinical response or the patient is up to pimozide, should be started at 1 mg daily, and increased 5 mg/day, usually enough for the patient to expect great every 5 to 7 days to a total of 3 mg to 6 mg daily divided into Clinical response should be measured by the 2 After the titration, the total dose can be taken at improvement in symptoms of formication and agitation. The bedtime. The most common side effects from risperidone patient generally does not relinquish the delusion of infesta- include rhinitis, dizziness and anxiety. The medication is also tion, but often will experience great relief and may even feel associated with dose-dependent sedation, fatigue and QT in- Possible side effects of pimozide include extrapyramidal side effects and QT As a result, a baseline Another second generation antipsychotic which has been EKG may be performed, especially if the patient is elderly or shown to be effective in treating delusions of parasitosis is has a history of arrhythmia. The EKG may then be repeated This medication is started at 5 mg to 10 mg when the patient has reached the therapeutic dose. If the cor- daily and increased to 10 mg to 15 mg daily. The most com- rected QT interval is prolonged to 520 milliseconds (or Ͼ25% mon side effects include sedation, anticholinergic effects (dry mouth, blurry vision, urinary hesitation, constipation), and One possible extrapyramidal side effect is akathisia, a sub- jective feeling of inner restlessness. Akathisia often manifests Even though starting treatment in delusions of parasitosis as pacing, fidgeting, foot tapping and/or an overall inability to can present a clinical challenge, response to treatment is usu- remain Another possible side effect is muscle stiffness.
ally robust. In a systematic review of 1,233 cases of delusions In order to help with these extrapyramidal side effects, pa- of parasitosis treated with an antipsychotic agent, 50% tients can take diphenhydramine (Benadryl) 25 mg 3 times a showed complete An even higher rate of remis- day as needed or benztropene (Cogentin) 1 to 2 mg every 6 sion was reported by a retrospective study in which 12 of 15 hours as needed. Patients should be counseled about the patients treated with antipsychotics achieved complete re- possibility akathisia and be prepared with one of these med- The increased rate of remission in this study may be ications before starting pimozide. If the side effects are con- due to the emphasis placed on development of therapeutic trolled, it is even okay to increase the dose of pimozide grad- rapport. For example, the treatment team included derma- tologists, psychiatrists, and patients’ spouses working to- Once the patient has achieved an optimal clinical re- gether in the same office to optimally manage the patient.
sponse, maintain the dosing for 2 to 3 months. At this point, In conclusion, delusion of parasitosis is an important con- one can attempt to taper pimozide 1 mg every 1 to 4 weeks, dition for the dermatologist to know how to handle as these titrating to the minimum effective dose or off the medication patients present a real challenge for proper management.
altogether. A reasonable expectation for the total length of However, once a therapeutic alliance is established, the Delusions of parasitosis
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