Updated: Feb 12, 2008
Delusions of parasitosis (DP) manifest in the patient's firm belief that he or she has pruritus due to an infestation with insects. Patients may present with clothing lint, pieces of skin, or other debris contained in plastic wrap, on adhesive tape, or in matchboxes. They typically state that these contain the parasites; however, these collections have no insects or parasites. This presentation is called the matchbox sign, or what the authors term the "Saran-wrap sign."
The patients have no obvious cognitive impairment, and abnormal organic factors are absent. True infestations and primary systemic diseases that cause pruritus are not involved. Primary skin lesions are not present. Physical examination may reveal no lesions, but only linear erosions with crusts, prurigo nodularis, and/or ulcers.
The classification of DP is complicated. It is considered primarily a monosymptomatic hypochondriacal psychosis and has been associated with schizophrenia, obsessional states, bipolar disorder, depression, and anxiety disorders. DP occurs primarily in white middle-aged or older women, although it has been reported in all age groups and in men.
Medscape Resource Centers for Schizophrenia, Bipolar Disorder, Depression, and Anxiety Disorders may provide helpful additional information.
Savely et al1 introduced the term Morgellon disease to describe a condition characterized by fibers attached to the skin. The entity appears to be little more than a new designation for DP. Koblenzer2 and Waddell and Burke3 have discussed the utility of the term, with Murase et al4 finding the term useful for building a therapeutic alliance with patients with DP. The Centers for Disease Control and Prevention is currently investigating Morgellon disease.5
William Harvey6 of the Morgellons Research Foundation Medical Advisory Board states the following:
The author of this article has not found reliable data to back up William Harvey's claims, but they are included here to comprehensively address this issue.All patients with Morgellons carry elevated laboratory proinflammatory markers, elevated insulin levels, and verifiable serologic evidence of 3 bacterial pathogens. They also show easily found physical markers such as peripheral neuropathy, delayed capillary refill, abnormal Romberg’s sign, decreased body temperature, and tachycardia. Most importantly they will improve, and most recover on antibiotics directed at the above pathogens.
The cause of DP is unknown. It appears related to neurochemical pathology. This concept is underlined by its induction by psychoactive agents (eg, amphetamines, cocaine, and methylphenidate) and its coincidence with depression, schizophrenia, social isolation, and sensory impairment.
The exact prevalence of DP is unknown.
The exact prevalence of DP is unknown.
The literature includes one report of suicide in a 40-year-old man with DP.8
DP appears to be more common in whites than in people of other races.
DP occurs primarily in white middle-aged or older women, although it has been reported in all age groups and in men. The female-to-male ratio is approximately 2:1. More specifically, this ratio is 1:1 in people younger than 50 years and 3:1 in those older than 50 years.
This disease is more common in middle-aged and elderly persons than in others. The male-to-female ratio is 1:1 in people younger than 50 years and 3:1 in those older than 50 years.
Patients must be queried about their symptoms, the duration of symptoms, and their belief about the etiology. Notably, Goddard9 has described a seasonality to DP.
The diagnosis and treatment of DP can be an involved clinical activity. Patients with DP can resist suggestions that their condition is psychiatric rather than physical and refuse referrals for psychiatric care. In fact, in 35% of patients, the belief of infestation is unshakable. In approximately 12% of patients, the delusion of infestation is shared by a significant other. This phenomenon is known as folie à deux (eg, craziness for 2) or folie partagé (ie, shared delusions). Variations in this are the conviction that a child, a spouse, or a pet is infested.
DP is a monosymptomatic psychosis, a type of psychopathology relatively distinct from the remainder of the personality. If the condition has a defined pathologic or external cause (eg, scabies) it is not truly DP. In investigating the history of a patient with such suspected delusions, other causes of itch must be investigated. To diagnose this condition, true infestations (eg, scabies), pediculosis, and primary systemic causes of pruritus must be excluded. Examples include hepatitis, HIV infection, dermatitis herpetiformis, thyroid disease, anemia, renal dysfunction, neurologic dysfunction, and lymphoma.
DP is distinct from formication. Formication involves the cutaneous sensation of crawling, biting, and stinging. Formication does not involve the fixed conception that skin sensations are induced by parasites. Patients with this condition can accept proof that they do not have an infestation. Many cases of formication remain idiopathic.
Mimics of DP
Other forms of psychiatric illness can mimic DP. Such psychiatric illnesses are accompanied by signs of mental illness.
For example, patients with schizophrenia may think they are being attacked by insects as a manifestation of their paranoia.
A type of severe depression termed psychotic depression may cause the patient to believe he or she is contaminated or "dirty" because of insect infestation. Such a patient may have a depressed mood and a sense of helplessness, hopelessness, worthlessness, or excessive guilt. Often, these feelings are obvious at clinical presentation.10
Drug-induced delusions of parasitosis have been reported during treatment for Parkinson disease.11
Steinert and Studemund12 reported a 45-year-old man who did not have a history of psychological pathology, who, after ingesting ciprofloxacin to treat an infection, was overcome with acute delusional parasitosis. He stopped taking the ciprofloxacin, and the DP resolved altogether without utilization of an antipsychotic agent. Cases in which an etiology is defined are best classified as secondary DP.
Guarneri et al13 noted a patient who was thought to have DP but who, in fact, had infestation with Limothrips cerealium; they termed the condition pseudo-delusory syndrome (ie, infestation with an uncommon insect).
Ghaffari-Nejad and Toofani14 noted a case of secondary DP in a patient with major depressive disorder who had delusions of oral parasitosis; the patient sensed lizards and small organisms in her mouth.
Patients with DP create their skin rash. They can present with no findings, erosions or ulcers with or without crusts or prurigo nodularis. They may evidence a dermatitis related to attempted treatments, which may include irritating or corrosive cleansers or harsh abrasive devices.
Dermatitis Herpetiformis
Scabies
Internal disease
Lymphoma
Cocaine-Related Psychiatric Disorders
DP has no specific histologic findings. All skin changes are secondary to rubbing, scratching, picking, or other treatment attempts.
The only clear method to clear the delusion that underlies DP is the administration of psychotropic medications. However, the disease can remit on its own. If the sensation of itch is related to some actual disease or substance use rather than a monosymptomatic hypochondriacal psychosis, the disease can be treated, or the substance inducing the sensation can be eliminated.
It is vitally important that the practitioner does not "use the delusion" to encourage the patient to accept certain treatments. While getting the patient to take a medication, such as risperidone, may help the condition, telling them that it is a medication that "kills the parasites", reinforces and validates the delusion. Even giving the patient a course of topical permethrin "just in case" may strengthen the delusion and make it that much more difficult later on. Every DP patient can recount the visit on which his or her suspicions of infestation were "confirmed."
Serotonergic antidepressants may have a role in the treatment of these patients.15,16
Reichenberg et al17 reported on a patient whose DP was cured overnight by having him stop taking cetirizine and doxepin (25 mg), as well as any over-the-counter medications.
Rocha and Hara18 reported that aripiprazole at 15 mg for 8 weeks and then 7.5 mg/d was effective for DP treatment. They stated:
Szepietowski et al19 sent out 172 specially designed questionnaires to dermatologists regarding DP patients; 118 responded. The questions and resulting percentages are as follows:Aripiprazole has a unique pharmacologic profile that is different from other atypical antipsychotic drugs. It is considered a partial dopaminergic agonist acting on both postsynaptic dopamine D2 receptors and presynaptic autoreceptors. It acts as a weak stimulator (so-called “partial” agonist) at dopamine D2 receptors, with the potential for exerting either antagonistic (inhibitory) or agonistic (stimulating) effects, depending on the sensitivity of the receptors and availability of dopamine, its natural agonist in the brain. In addition, aripiprazole displays partial agonism at serotonin (1A) receptors and antagonism at serotonin (2A) receptors.
A psychiatrist should be consulted if the dermatologist cannot or will not prescribe the necessary medications. Most patients with DP are reluctant to see a psychiatrist, and the dermatologist may be more successful in giving the referral if they have gained the patient's trust after several clinic visits instead of immediately after meeting the patient.
The current treatment of choice is risperidone20,21 or olanzapine.22 The older treatment of choice is pimozide.23
The most common adverse effects of pimozide are extrapyramidal symptoms, including stiffness and, occasionally, a special inner sense of restlessness called akathisia. Effective treatment of such extrapyramidal reactions includes benztropine 1-2 mg up to 4 times daily as needed or diphenhydramine 25 mg 3 times daily.
Used to treat psychoses.
Binds to dopamine D2 receptor with 20 times lower affinity than for 5-HT2 receptor. Improves negative symptoms of psychoses and reduces incidence of extrapyramidal adverse effects.
1-2 mg qd initially
Not indicated
Coadministration with carbamazepine may decrease effects; risperidone may inhibit effects of levodopa; clozapine may increase risperidone levels.
Hypersensitivity
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
May cause extrapyramidal reactions, hypotension, tachycardia, and arrhythmias
May inhibit serotonin, muscarinic and dopamine effects.
2.5 mg/d
Not indicated
Fluvoxamine may increase effects of olanzapine; antihypertensives may increase risk of hypotension and orthostatic hypotension; levodopa, pergolide, bromocriptine, charcoal, carbamazepine, omeprazole, rifampin, and cigarette smoking may decrease effects of olanzapine.
Documented hypersensitivity
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Caution in narrow-angle glaucoma, cardiovascular disease, cerebrovascular disease, prostatic hypertrophy, seizure disorders, hypovolemia, and dehydration
Antipsychotic of the diphenylbutylpiperidine class. It is used to treat DP and Tourette disorder.
1-12 mg/d
<12 years: Not established
>12 years: Administer as in adults
Increases toxicity of MAOIs, alfentanil, CNS depressants, and guanabenz
Documented hypersensitivity; history of cardiac arrhythmias or long QT syndrome; presently receiving macrolide antibiotics
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
ECG recommended at initiation and regular intervals thereafter; careful observation for extrapyramidal symptoms, especially in geriatric patients
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DP, DOP, insect infestation, matchbox sign, monosymptomatic hypochondriacal psychosis, delusion of infestation, delusional parasitosis, delusional infestation, folie à deux, folie partagé, morgellons disease.
Noah S Scheinfeld, MD, JD, FAAD, Assistant Clinical Professor, Department of Dermatology, Columbia University; Consulting Staff, Department of Dermatology, St Luke's Roosevelt Hospital Center, Beth Israel Medical Center, New York Eye and Ear Infirmary; Private Practice
Noah S Scheinfeld, MD, JD, FAAD is a member of the following medical societies: American Academy of Dermatology
Disclosure: Nothing to disclose.
Franklin Flowers, MD, Chief, Division of Dermatology, Professor, Department of Medicine and Otolaryngology, University of Florida College of Medicine
Franklin Flowers, MD is a member of the following medical societies: American College of Mohs Micrographic Surgery and Cutaneous Oncology, Lipoplasty Society of North America, Southwest Pediatric Nephrology Study Group, Southwestern Oncology Group, Southwestern Surgical Congress, Special Operations Medical Association, State Medical Society of Wisconsin, Swedish Medical Association, Sydenham Society, Tennessee Medical Association, Tennessee Radiological Society, Texas Medical Association, Texas Pediatric Society, Texas Society of Plastic Surgeons, Undersea and Hyperbaric Medical Society, Uniformed Services Academy of Family Physicians, United States and Canadian Academy of Pathology, United States Pharmacopeial Convention, US Virgin Islands Medical Society, Utah Medical Association, Vermont State Medical Society, Vestibular Disorders Association, Virginia Society of Otolaryngology-Head and Neck Surgery, West Virginia State Medical Association, Western Occupational and Environmental Medical Association, Western Orthopaedic Association, Western Section American Urological Association, Western Surgical Association, Wilderness Medical Society, World Association of Societies of Pathology and Laboratory Medicine, World Medical Association, World Society for Stereotactic and Functional Neurosurgery, and Wyoming Medical Society
Disclosure: Nothing to disclose.
David F Butler, MD, Professor of Dermatology, Texas A&M University College of Medicine; Director, Division of Dermatology, Scott and White Clinic; Director Dermatology Residency Training Program, Scott and White Clinic
David F Butler, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Dermatology, American Medical Association, American Society for Dermatologic Surgery, American Society for MOHS Surgery, Association of Military Dermatologists, and Phi Beta Kappa
Disclosure: 3M Pharmaceutical Grant/research funds Other; Graceway Pharmaceuticals Grant/research funds Other
Jeffrey Meffert, MD, Assistant Clinical Professor of Dermatology, University of Texas Health Science Center-San Antonio
Jeffrey Meffert, MD is a member of the following medical societies: American Academy of Dermatology
Disclosure: Nothing to disclose.
Catherine Quirk, MD, Clinical Assistant Professor, Department of Dermatology, Brown University
Catherine Quirk, MD is a member of the following medical societies: Alpha Omega Alpha and American Academy of Dermatology
Disclosure: Nothing to disclose.
Dirk M Elston, MD, Director, Department of Dermatology, Geisinger Medical Center
Dirk M Elston, MD is a member of the following medical societies: American Academy of Dermatology
Disclosure: Nothing to disclose.
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