What is delusional parasitosis

Delusional parasitosis also called Ekbom syndrome, is a rare psychiatric disorder classified in the DSM 5 under the delusional disorders where an individual has the mistaken belief that they are being infested by parasites such as mites, lice, fleas, spiders, worms, bacteria, or other organisms ¹. Delusions of parasitosis is a fixed false belief that the patient has an infection with an organism such as parasites or other nonvisible organisms ². Delusions of parasitosis are sometimes called delusional infestation, psychogenic parasitosis, pseudoparasitic dysaesthesia, or parasitophobia. Delusional parasitosis is closely related to Morgellons disease, in which an individual feels they have fibers coming out of their skin.

Delusions of parasitosis are relatively uncommon ³. Psychiatrists and dermatologists rarely see the disorder as patients do not believe that their symptoms are a delusion, but instead based in reality ³. Previous studies have found different rates of incidence ranging from 1.9 to 27.3 cases per year per 100000 people ⁴. The average age of the patient at diagnosis was found to be between 57 to 61.4 years of age on previous studies, suggesting an increased prevalence with increased age ⁴. Some studies found a greater incidence in females than males, but this gender prevalence did not appear in other research ⁵.

The most common symptoms typically presented by patients include pruritus, rashes, stinging, or formication with symptoms lasting six months or longer and having no physical findings present. Patients may have had previous trials of topical dermatologic medications and/or antibiotics in attempts to treat the illness. Patients may also have their pets evaluated to rule out fleas or mites with concerns that the pets may have transferred those to the patient. Patients can provide exhaustive histories revolving around false descriptions of parasites, the timing of infestations, and even prior trials of attempting to have pest control treatment of their homes. Other studies also demonstrated that patients might draw family members or friends into their delusions in 15 to 25 percent of cases resulting in a folie à deux (craziness of 2) ⁶. Patients presenting with complaints and symptoms of delusions of parasitosis often will maintain functionality but frequently develop feelings of frustration and helplessness ².

The diagnosis is a delusional disorder where the patient experiences a fixed, false belief that they have an infection with a parasite, worms, mites, bacteria, fungus other types of living organisms ². Patients are resistant and difficult to reason with to alter their thinking about their belief in the delusion. The initial literature to describe delusional parasitosis appeared in 1948. There are two forms of delusions of parasitosis: primary and secondary ⁷. The primary form of the illness is a psychiatric disorder where the delusions of parasitic infection are the only symptom present ⁸. The secondary variety is when the delusions of parasitosis occur alongside another psychiatric disorder such as schizophrenia or secondary to drug abuse or medical illness ⁸.

Delusional parasitosis causes

Most commonly, delusions of parasitosis present secondary to a primary psychiatric disorder. These disorders include schizophrenia, bipolar disorder, depression, anxiety, obsessive-compulsive disorder, and illness anxiety disorder ⁹.

Secondary delusions of parasitosis can have several medical causes. These causes include ¹⁰:

• Medical illnesses such as hyperthyroidism, B12, and folate deficiencies, neuropathy, and diabetes
• Neurologic conditions such as dementia, stroke, multiple sclerosis, encephalitis, meningitis, and post-surgical complications from neurosurgery
• Substance abuse including methamphetamine use, alcohol withdrawal, and acute cocaine use (described as “cocaine bugs”)
• Infectious causes such as HIV, tuberculosis, leprosy, and syphilis
• Medication side effects from medications such as topiramate, ciprofloxacin, amantadine, steroids, ketoconazole, and phenelzine

The pathophysiology behind delusions of parasitosis is poorly understood. A hypothesized mechanism includes a possible increase of extracellular dopamine within the striatum of the brain that could be the result decreased functionality of dopamine transporters to facilitate the transport of the neurotransmitter ¹¹. Favorable patient responses to dopamine antagonists as a treatment for the disorder bolster this theory ¹².

Delusional parasitosis symptoms

People suffering from delusions of parasitosis often describe the infestation as being in or under the skin, just inside body openings or in sputum, inside their stomach or intestines, and in their surrounding habitat such as their bed, couch or throughout their home.

Characteristic symptoms of delusions of parasitosis include:

• A patient seeking numerous opinions from medical doctors, exterminators, hygienist and entomologists, then often complaining about the incompetence of the advice received and treating the specialist with hostility and suspicion.
• Sensations of itching, burning, crawling and biting that may lead to self-mutilation as the sufferer attempts to dig out the parasites. This causes minor scratches to gouged out pits and ulcers.
• Exhibit the “matchbox sign” (also called “specimen sign”) which is where the sufferer offers for examination specimens kept in a small container such as a matchbox. Specimens usually consist of fragments of skin, hair, dried blood or scabs. Sometimes they may include living organisms such as ants or flies.
• Extreme measures may have been taken to cleanse the skin and to disinfect or even destroy clothing and furniture.

One or more family members sometimes share delusions of parasitosis. When two family members are involved, usually husband and wife or parent and child, the delusion is known as folie à deux (craziness of 2).

Delusional parasitosis complications

Delusions of parasitosis can present a few common complications. A delay in treatment can lead to superficial scarring on the patient’s skin and a possible decrease in function ¹³. A small study reported that patients with delusions of parasitosis also had increased incidents of self-inflicted keratoconjunctivitis ¹⁴. Another significant complication in the treatment of the illness is the side effects of antipsychotic medications, including extrapyramidal symptoms, QT prolongation, weight gain, and other metabolic effects ¹⁴. The second generation, atypical antipsychotics are preferred compared to typical antipsychotics for a more favorable side effect profile.

Delusional parasitosis diagnosis

Complete physical examination and appropriate laboratory tests can help to identify other diseases that mimic the delusions of parasitosis and rule out any true infestations, e.g. with scabies or lice.

• Skin scrapings and biopsies
• Complete blood count
• Chemistry profile
• Thyroid function tests
• Mineral and vitamin measurements, e.g. vitamin B12, ferritin (iron)

A history of drug abuse with cocaine, methylphenidate, or amphetamines must also be ascertained as these substances can induce the sensation of itchiness and result in skin picking.

Delusional parasitosis treatment

The management of patients with delusions of parasitosis is often difficult as they are totally convinced of the existence and infestation of “their” parasites. Sometimes the disease may get better and go away on its own but in most cases, treatment with psychotropic medications is usually necessary. Often management of these patients is best handled through the cooperation of dermatologists, psychiatrists and entomologists. The following points should be taken into consideration when treating a patient.

• Considerable tact and repeated visits are needed to gain the patient’s trust before broaching the actual existence of the infestation and noting that the problem is a psychiatric illness.
• Do not “use the delusion” to encourage patients to accept certain treatments. For example getting a patient to take a psychotropic drug by telling them that this will “kill the parasites” only reinforces and validates their delusion.
• Sufferers are often reluctant to seek psychiatric help, and if suggestions to do so by a doctor or dermatologist are not made carefully, the patient may not return for future visits.
• Some patients may be able to live with their infestation without drug or psychiatric treatment by receiving appropriate reassurance, support and attention from their doctor or dermatologist.
• Depressive symptoms should be screened for and treatment of depression may be useful. Escitalopram, a selective serotonin reuptake inhibitor, has been reported effective.
• Antipsychotics such as pimozide, risperidone and olanzapine have all been used but should only be started under supervision from a dermatologist or psychiatrist.

Once the clinician has made a diagnosis of delusions of parasitosis, the primary consideration in treatment is to build a strong rapport with the patient and maintain a good relationship. Patients can feel frustrated and disrespected and untrusting of practitioners who do not take the time to listen to their complaints or symptoms, which can lead to noncompliance with follow up care and visiting alternative practitioners for second opinions. Practitioners should focus on being objective and acknowledging the patient’s symptoms, not dismissing their symptoms or feelings, and understanding the effect this can have on their daily life. Agreeing or disagreeing with the patient overtly in the office about their symptoms can be a difficult decision to make. The most accepted approach involves taking a neutral approach by stating that there are no organisms visible to the practitioner at this time but that they may have been present before ³. It is imperative for practitioners not to dismiss patient complaints, but at the same time being careful not to perpetuate the delusion that can further bolster and strengthen it making treatment more difficult ³.

Rejecting a psychiatric origin of symptoms is common in patients. Patients are often reluctant to take medications for the management of symptoms. Recommendations are that practitioners tell the patient that symptoms are secondary to altered chemicals in the brain in the hope that they are more likely to comply with the use of medications. Patients will often need reassurance that antipsychotic drugs are not being used for the treatment of schizophrenia or other psychotic conditions, as this can be a turn-off for patients. Patients need education regarding alternative uses of antipsychotic medications through an explanation of the mechanism of action of the medication. Also indicating to patients that studies have shown that patients have had success with the proposed treatment can improve compliance.

First generation antipsychotics, such as pimozide were widely used in the treatment of delusions of parasitosis in the past but are no longer recommended as a first-line treatment due to adverse side effects ¹⁵. The opioid blocking mechanisms were theorized to improve symptoms of pruritus and formication making the medication an attractive choice ¹⁶. The side effect profile of first generation antipsychotics versus second-generation antipsychotics makes a clear choice of not choosing an first generation antipsychotic as first-line treatment.

First line treatment for delusions of parasitosis consists of antipsychotics at lower doses that minimize side effects ¹⁶. If patients have a relapse of symptoms after discontinuation of antipsychotic medication, they should restart the therapy ³. Recommended second-generation antipsychotics include quetiapine, olanzapine, risperidone, and aripiprazole. These medications should be employed at the lowest possible dose to prevent side effects including extrapyramidal symptoms, QT prolongation, and metabolic side effects ¹⁶. Newer antipsychotics such as lurasidone, paliperidone, and brexpiprazole could be attractive medication choices due to their lower rate of side effects but do not have any significant evidence supporting their use in delusions of parasitosis, and their cost can be a drawback ¹⁷.

Delusional parasitosis prognosis

Delusions of parasitosis generally do not inhibit the patient’s ability to function, but rather serve as a hindrance and persistent symptom. However, for some patients, delusions can decrease their life quality significantly ². Patients generally have good response rates to atypical antipsychotic treatments ¹⁶. Patients can typically be tapered off medications over weeks and can respond well if symptoms reappear with the reintroduction of treatment ¹⁸. Studies have demonstrated successful response rates to antipsychotic treatment of delusion of parasitosis from 60 to 100 percent ¹². Treatment of secondary causes of delusions of parasitosis should focus on treating the underlying condition with consideration of possible adjunct antipsychotic treatment for the management of symptoms if needed.

References

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