Printer Friendly

Delusional infestations: case series, differential diagnoses, and management strategies.

In an era of Internet-assisted self-diagnoses and the return of bedbugs, physicians are not infrequently consulted by distraught patients who believe that they are infested with external or internal parasites, describe a crawling sensation of bugs or worms on or under their skin, and often display a boxed specimen or blurred photo of the offending parasite. When other causes of infectious dysesthesias --such as scabies, cercarial dermatitis, and cutaneous larva migrans--are excluded by physical examination or skin biopsy, and no treatable dermatoses are diagnosed, this condition is called delusional infestation, formerly delusional parasitosis. The objectives of this review are to present a representative series of cases of delusional infestations and to recommend effective management strategies.


Internet search engines were queried with the keywords as search terms to examine the latest scientific articles on delusional infestations in order to describe a variety of clinical and behavioral manifestations, develop a differential diagnosis, and recommend new and effective management strategies. The keywords included the following: parasitosis, delusional; ectoparasitosis, delusional; infestations, delusional; Ekbom's syndrome; acarophobia; and Morgellons disease. A representative series of cases, either from peer-reviewed scientific publications, or from the authors' own clinical practices are reported first.


Report of Cases

Case 1 (Adapted from Meehan WJ et al. 2006) (1)

A 56-year-old female with a history of depression presented with a two-month history of intensely pruritic sensations of "bugs that were crawling" on her posterior neck at her hairline. These sensations were resistant to topical therapy with antihistamines and corticosteroids. Physical examination demonstrated a localized plaque of self-excoriated nodules and papules. Microscopic examination of skin scrapings was negative for scabies mites or eggs, and a potassium hydroxide mount was negative for any organisms or fungi. Intralesional triamcinolone was injected into the largest nodule, and the patient was instructed to apply a topical steroid cream twice daily to the affected area and to complete a 10-day course of oral cephalexin before returning for follow-up. At follow-up, the patient was tearful and distraught and produced a specimen of a "bug" from her hairline, later identified as a dried pea. The patient was started on oral atypical antipsychotic therapy with olanzapine, 5 mg/day, and demonstrated dramatic improvement and resolution of all symptoms at her one-month follow-up appointment.

Case 2 (Author's case)

A physician and his wife experienced episodic crawling sensations on their faces, chests, and backs, especially at night, and developed an increasing number of pruritic, papular lesions in the same locations that became excoriated from scratching. Dermatoscopic examination of the lesions and microscopic examination of skin scrapings from the lesions revealed no evidence of scabies or mite infestations. A pest extermination company examined the premises and found no evidence of animal or arthropod infestation, and a veterinarian found no evidence of ectoparasitic infection on examination of the family's pet dog. Later, the episodes of pruritic crawling sensations in similar locations causing self-excoriations occurred in other family members in other areas of the residence. The physician treated his family with oral ivermectin and topical permethrin and the family's pet dog with topical permethrin. The family then spent two nights in a hotel while their house was being professionally fumigated with a pyrethroid pesticide. On return to the household, the pruritic crawling sensations had improved but persisted. There was no further follow-up.

Case 3 (Author's case)

A 45-year-old nurse, who lived with two cats in an apartment whose carpets had been treated for carpet beetles, developed pruritic bite-like lesions with scratch marks on the anterior abdominal wall and breasts. Microscopic examination of skin scrapings and potassium hydroxide mounts demonstrated no evidence of scabies mites or eggs, or other arthropods, or fungi. Repeated examination of the two cats by a veterinarian demonstrated no evidence of ectoparasitic infections. After moving to another apartment in an old home with a basement, the patient reported fewer episodes of itching with topical antihistamine therapy until mice were discovered and trapped in the basement and moths were identified in her bedroom. Following control of the mice and moths by an exterminator, the itching and scratch marks improved again. Lastly, the patient also reported excessively vacuuming of the carpets and was later lost to follow-up.

Case 4 (Adapted from Donabedian H 2007) (2)

A 51-year-old dog breeder whose dogs had been treated for ectoparasites several months earlier reported to an infectious disease specialist that she had "worms crawling under her skin" that occasionally exited her skin, jumped into her nose or eyes, and then traveled to her brain causing severe headaches. The physical examination and all laboratory tests were negative, including a serologic test for leptospirosis. Later, the patient produced a sealed plastic bag containing round "worms" rolled in tissue paper. Microscopic examination demonstrated the "worms" to be inanimate, fiber-like matter. When a recommendation was made for psychiatric consultation and possible treatment with antipsychotic medications, the patient accused the physician of being totally uncaring of her suffering and completely ignorant of her condition. The patient dismissed her physician and was lost to further follow-up.


The earliest reports of delusions of infestations were published in the late 19th century and attributed to Thibierge, who reported cases of "acarophobia." (2) In 1938, Karl Ekbom, a Swedish neurologist, described "delusions of animals on the skin," but his long German description was so cumbersome (Dermatozoenwahn) that the condition was called Ekbom's syndrome instead until 1946, when Wilson and Miller coined "delusion of parasitosis." (3) More recently, Freudenmann and Lepping have recommended a broader term, "delusional infestation," rather than more disease-oriented descriptions, such as parasitosis and phobia. (4)

Approximately 5%-15% of patients with delusional infestations will exhibit delusions shared with a spouse or relative (folie a deux) or shared with more than one family member or close friend (folie partage). (5) The most common shared delusions are between husband and wife; between siblings, especially twins; or between a parent, usually the mother, and a son or daughter. (2,5) Patients with delusional infestations all harbor intense anger and resentment for physicians who do not quickly confirm their perceived infestations. They will dismiss their initial doctors quickly to seek other medical opinions from a variety of specialists ranging from dermatologists to internists and infectious disease specialists. (2)

In 1992, Bourgeois and coauthors reported a case of shared delusional infestations between husband and wife (folie a deux) in which a 58-yearold woman was institutionalized for attempting to kill her general practitioner who refused to confirm her delusions. (5) In some cases, patients with delusional infestations have killed their pets to rid themselves of their perceived delusions. (2)

All of the cases presented in this series have demonstrated the pathognomonic behavioral features and clinical manifestations of delusional infestations, including: (1) onset in well-educated, middle-aged adults who are pet owners (Cases 2, 3, and 4); (2) production of purported specimens of causative parasites in what is called the "matchbox sign" (Cases 1 and 4); (3) pesticide overtreatment of themselves, their households, and their pets with oral (ivermectin) and topical (ivermectin, pyrethroids) insecticides (Cases 2 and 3); (4) excessive cleaning or vacuuming of their households (Case 3); (5) intense anger and resentment directed towards physicians failing to confirm their self-diagnoses (Case 4); and (6) sharing delusional symptoms with their spouses or partners in the folie a deux phenomenon (Case 2), or with others in the folie partage phenomenon (Case 2). (1,2)

In addition, Case 4 demonstrated a unique variation of delusional infestation, now known as Morgellons disease or syndrome, by producing "round worms" rolled in paper tissues. (6) Morgellons disease is defined as an unrecognized medical and/or neuropsychiatric disorder in which embedded fibers of cellulose or cotton from clothing or paper can be demonstrated microscopically in self-excoriated, intensely pruritic and self-excoriated skin lesions in patients suffering from delusional infestations. (6)

In 1995, Trabert reported the results of his comprehensive meta-analysis of 193 reports of delusional infestations over 100 years that included 1,123 case-patients. (7) The incidence in Germany was 1.6 cases per million cases per year with a mean age of case-patients of 57 years. (7) The ratio of female-to-male cases was 1.4:1.0 for those under age 50 years and 2.5:1.0 for those 50 years of age and older. (7) Subsequent descriptive and analytical epidemiological investigations, including our own small case series, have confirmed similar demographic characteristics. (8) When Reilly and Batchlor surveyed 386 dermatologists in the United Kingdom, 66% reported seeing at least one patient with delusional infestation within the past five years. (8)

The major differential diagnoses of delusional infestation include true ectoparasitic infections and cutaneous larva migrans, which must be ruled out initially by careful recreational, occupational, and travel histories, microscopic and laboratory tests, and drug-induced or neurological disease associated dysesthesias (Table 1). Ectoparasitic infections, such as scabies and animal mite infestations, may occur in large seasonal clusters, such as in Pittsburg, Kansas, in August 2004, when 300 residents sought immediate medical care for intensely pruritic, erythematous, papular rashes that were subsequently determined to be caused by multiple bites from European itch mites (Peymotes herfsi) (Figure 1). (9) These insect mites are ectoparasites of leaf-rolling fly larvae that fall from oak trees or get carried by the wind and land on people outdoors, causing summertime community outbreaks of pruritic rashes. (9)

Another common cause of seasonal clusters of pruritic rashes may be caused by aquatic exposures to the infective stage cercariae of several avian schistosomes, or flatworms, that are released into freshwater lakes and rivers in the tens of thousands by infected aquatic snail intermediate hosts in a complicated life cycle (Figure 2). Cercarial dermatitis, or swimmer's (duck hunter's) itch, has occurred in seasonal outbreaks in swimmers in freshwater lakes and rivers whose resident or migratory waterfowl are infected with avian schistosomes (Figure 3). Lastly, several drugs; metabolic disorder-associated peripheral neuropathies, especially diabetic neuropathy; and some neurodegenerative diseases, especially Parkinson's and Alzheimer's diseases; can cause dysesthesias with bug-crawling skin sensations that mimic arthropod infestations (Table 1). (1,2,10,11)

Prior to the discovery of antipsychotic medications, Wilson and Miller reported a poor prognosis for patients with delusional infestations with 82% of 51 reported patients having no change in their illnesses. (3) However, by the 1990s and with the use of the first generation or typical antipsychotics in managing delusional infestations, especially pimozide, Trabert reported nearly 70% improvement in patients with pharmacotherapy. (7,12)

Today, the best management strategies for patients with delusional infestations include careful and empathetic work ups for evidence of parasitosis, psychological counseling, and the use of the newer neuroleptic medications, especially the second-generation or atypical antipsychotic medications, including olanzapine, risperidone, and ziprasidone. (1,2,16-19) Unlike pimozide and all other first-generation antipsychotics, the second-generation antipsychotics carry less risk of precipitating cardiac arrhythmias, especially prolonged QT intervals and torsades de pointes, extra-pyramidal syndromes, and tardive dyskinesias. (1,12-14)

Several reports have now confirmed that relatively small daily doses of these atypical antipsychotics or neuroleptics are dramatically effective in reducing the delusions of infestation. (1,13,14) Some of the atypicals are associated with sedation, weight gain, and hyperglycemia, especially olanzapine; but all have significantly lower potentials for causing cardiac arrhythmias, extrapyramidal syndromes, and tardive dyskinesias than the first generation antipsychotics. (1,13,14) Table 2 compares the adverse effects of the second-generation antipsychotics recommended for the management of delusional infestations and their dosing schedules.

In 2006, Narumoto and co-investigators reported a case that has now provided significant scientific support for a physiochemical mechanism of dopaminergic and serotonergic neurotransmitter dysfunction in delusional infestation and for the continued use of second-generation antipsychotics in treating the disorder. (14) In their case, a patient developed delusional infestation following an acute, ischemic stroke in the right temporoparietal region and was treated with risperidone with rapid, dramatic improvement. (14) A pre-treatment single-photon emission computerized tomography (SPECT) scan showed a global decrease in regional cerebral blood flow (rCBF), but a post-treatment scan showed marked increase in rCBF in the region of the brain infarct and in the basal ganglia bilaterally. (14) This report was the first objective confirmation using sensitive neuroimaging techniques of the utility of second-generation antipsychotics in the management of the disorder by increasing rCBF in specific brain regions. (14) In addition, the neuroimaging shady demonstrated an association between reduced rCBF and the dysesthesias of delusional infestation and the reversal of dysesthesias with the restoration of rCBF, suggesting an ischemic mechanism for the disorder. (14)

Although some reports have suggested that cases of delusional infestation are increasing today, especially in arid and tropical regions where arthropod-borne infectious diseases are hyperendemic, most studies have now confirmed a relatively stable incidence rate over time and similar disease demographics worldwide. (15) The management strategies for delusional infestations have, however, changed significantly over time with second-generation, atypical antipsychotics offering safer adverse effect profiles and better prognoses than earlier therapies with first-generation, typical antipsychotics. The most effective current management strategies for delusional infestations include empathetic history-taking and active listening to the patient; careful exclusion of true parasitoses, such as mite infestations and cercarial dermatitis, and neurodegenerative or cerebrovascular disorders; and a therapeutic regimen that includes a second-generation neuroleptic agent.


(1.) Meehan WJ, Badreshia S, Mackley CL. Successful heatarent of delusions of parasitosis with olanzapine. Arch Dermatol 2006; 142: 352-355.

(2.) Donabedian H. Delusions of parasitosis. Clin Infect Dis 2007; 45: 131-134.

(3.) Wilson JW, Miller HE. Delusion of parasitosis. Arch Dermatol Syphiol 1946; 54: 39-56.

(4.) Freudenmann RW, Lepping P. Delusional infestation. Clin Microbiol Rev 2009; 22: 690-732.

(5.) Bourgeois ML, Duhamel P, Verdoux H. Delusional parasitosis: folie a deux and attempted murder of a family physician. Br J Psychaitr 1992; 161: 709-711.

(6.) Pearson ML, Selby JV, Katz KA, et al. Clinical, epidemiologic, histopathologic and molecular features of an unexplained dermatopathy. Plos One 2012; 7: e29908. Doi: 10: 1371/journal. pone.0029908. Published January 25, 2012.

(7.) Trabert W. 100 years of delusional parasitosis. Psychopathol 1995; 28: 238-246.

(8.) Reilly TM, Batchlor DH. The presentation and treatment of delusional parasitosis: a dermatological perspective. Intl Clin Psychopharmacol 1986; 1: 340-353.

(9.) US Centers for Disease Control and Prevention. Outbreak of pruritic rashes associated with mites-Kansas, 2004. Morb Mort Week Rep 2005; 54: 952-955.

(10.) Fleury V, Wayte J, Kiley M. Topiramate-induced delusional parasitosis. J Clin Neurosci 2008; 15: 597-599.

(11.) Bhatia MS, Jhanjee A, Srivastava S. Delusional infestation: a clinical profile. Asian J Psychiatr 2013; 6: 124-127.

(12.) Reilly TM, Jopling WH, Beard AW. Successful freabment with pimozide of delusional parasitosis. Br J Dermatol 1978; 98: 457-459.

(13.) Gowda BSN, Heebar S, Sathyanarayana MT. Delusional parasitosis responding to risperidone. Indian J Psychiatr 2002; 44: 382-383.

(14.) Narumoto J, Ueda H, Tsuchida H, et al. Regional cerebral blood flow changes in a patient with delusional parasitosis before and after successful freahment with risperidone: a case report. Prog Neuropsychopharmacol Biol Psychiatr 2006; 30: 737-740.

(15.) Sabry AH, Fouad MA, Morsy AT. Entomophobia, acarophobia, parasitic dermatophobia or delusional parasitosis. J Egypt Soc Parasitol. 2012; 42: 417-430.

Dr. Diaz is Professor of Public Health and Preventive Medicine and Head, Program in Environmental and Occupational Health Sciences, Schools of Public Health and Medicine, Louisiana State University Health Sciences Center in New Orleans. Prior to publication of this article, Dr. Nesbitt Jr. passed away. He was Professor and Chair of the Department of Dermatology, School of Medicine, LSUUSC-New Orleans.

Table 1: The Differential Diagnosis of Delusional Infestations

Infections                            Drug-induced

Ectoparasitic infections:        Prescribed medications:

Scabies (Sarcoptes scabiei)      Ciprofloxacin
Follicle (Demodex) mites         Corticosteroids
Animal and plant mites           Phenelzine
Body lice (Pediculus humanus     Topiramate
Pubic lice (Pthirus pubis)

Cutaneous larva migrans:         Illicit drugs:

Animal hookworms (Ancylostoma    Cocaine
Avian schistosomal cercarial
  dermatitis (swimmer's itch
  or duck hunter's itch)

Miscellaneous infections:

Shingles (Herpes zoster)
Hansen's disease

Infections                                    Neurological

Ectoparasitic infections:        Parkinson's disease
                                 Alzheimer's disease
Scabies (Sarcoptes scabiei)      Diabetic neuropathy
Follicle (Demodex) mites         Morgellons disease (an unrecognized,
Animal and plant mites             self-diagnosed neuropsychological
Body lice (Pediculus humanus       disorder characterized by delusional
  corporis)                        infestation)
Pubic lice (Pthirus pubis)       Trichotillomania (a compulsive urge
                                   to pull out and, in some cases, eat
                                   one's own hair, usually on the

Cutaneous larva migrans:         Cerebrovascular disease:

Animal hookworms (Ancylostoma    Temporoparietal lobe infarcts
Avian schistosomal cercarial
  dermatitis (swimmer's itch
  or duck hunter's itch)
Miscellaneous infections:

Shingles (Herpes zoster)
Hansen's disease

Table 2: Second Generation Antipsychotics Recommended for Delusional
Infestations: Comparison of Dosing Schedules and Adverse Effects

Medications: generic names      Olanzapine        Risperidone

Medications: trade names        Zyprexa[R]        Risperdal[R]

Daily dosing schedule        5 mg po q day hs   2 mg po q day hs

Weight gain                        +++                 ++

Hyperglycemia                       +                  0

Dyslipidemias                       +                  0

Sedation                            ++                 ++

Hypotension                         +                  +

Anticholinergic effects            +++                 +

Medications: generic names           Ziprasidone

Medications: trade names              Geodon[R]

Daily dosing schedule         Advance over 2 days from
                             20 mg bid to 40 mg tid (120

Weight gain                              0/+

Hyperglycemia                             0

Dyslipidemias                             0

Sedation                                  +

Hypotension                               0

Anticholinergic effects                   +

+++ : High effect; ++ : Moderate effect; +: Minimal effect; 0: No
COPYRIGHT 2014 Louisiana State Medical Society
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2014 Gale, Cengage Learning. All rights reserved.

Article Details
Printer friendly Cite/link Email Feedback
Author:Diaz, James H.; Nesbitt, Lee T., Jr.
Publication:The Journal of the Louisiana State Medical Society
Article Type:Clinical report
Date:Jul 1, 2014
Previous Article:Calvarial plasmacytoma, an unusual manifestation of multiple myeloma.
Next Article:Surgical management of middle cerebral artery aneurysms.

Terms of use | Privacy policy | Copyright © 2019 Farlex, Inc. | Feedback | For webmasters