Delusional Infestation Surges During COVID-19 Pandemic

Bruce Jancin

February 05, 2021

Editor's note: Find the latest COVID-19 news and guidance in Medscape's Coronavirus Resource Center.

Psychiatrists with expertise in delusional infestation have some advice for dermatologists, infectious disease specialists, and primary care physicians who encounter affected patients: If you want to try to help them, initiate treatment yourself.

Dr Peter Lepping

"If you see it, try and treat it. These patients are unlikely to agree to see a psychiatrist," Peter Lepping, MD, said at the Entomology 2020 annual meeting.

Indeed, one of the hallmarks of delusional infestation (DI) is a refusal to even consider referral to a mental health professional, noted Lepping, a consultation-liaison psychiatrist at Bangor (Wales) University who, together with an infectious disease specialist, codirects one of the world's few DI multispecialty referral clinics, located at the University of Liverpool School of Tropical Medicine.

That being said, he offered another piece of advice: "Accept that it is not easy to help these patients."

Lepping was among a group of distinguished psychiatrists, dermatologists, entomologists, and a neurologist at the annual meeting who participated in a comprehensive session devoted to DI. The experts shared tips on making the diagnosis, establishing the rapport necessary to persuade affected patients to try taking a very-low-dose antipsychotic agent for their delusion, and how to achieve a high rate of therapeutic success. They also highlighted recent research advances in the field, including brain MRI evidence suggesting that impaired somatosensory neural networks mediate symptoms in DI, but not in nonsomatic delusional disorders.

COVID-19 Pandemic Triggers Surge in DI

Entomologist Gail E. Ridge, PhD, has taken notes on all of her thousands of consultations with individuals with suspected DI since the late 1990s. A sharp jump in such contacts occurred during the Great Recession of 2008 in conjunction with the widespread social distress of job loss and threatened economic ruin. Now the same thing is happening as the catastrophic COVID-19 pandemic stretches on. Indeed, during the first 8 months of the pandemic she documented 500 interactions involving people with suspected DI. She's learned to identify the clues, including a chattering mind, defensiveness, physician avoidance, and rigid body tension.

"They're fearful of judgment and suggestions of madness. And they'll pounce on any perceived negativity. I never debunk beliefs; that can immediately backfire. If the medical profession was educated about DI, then many cases could be caught early. I, as the entomologist, and the mental health professionals are often last in line to be seen," said Ridge, director of the Insect Information Office at the Connecticut Agricultural Experiment Station in New Haven.

She has noticed a recurring theme in her interactions with these patients: DI often starts with a real underlying medical condition, such as, for example, a cutaneous drug reaction, which over time, progresses to gain a psychiatric component. And she has found that a tipping point often occurs after roughly 6 months of unrelieved symptoms and sensations. Prior to that, affected individuals are concerned about their condition and will seek medical help in a genuine effort to understand what's going on. They can be redirected. After about 6 months, however, Ridge has observed "they slide into the rabbit hole of fanaticism and despair."

Arriving at the Diagnosis

In the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), DI is classified as a "delusional disorder, somatic type 297.1 F22." The diagnosis requires that the delusion be present for at least 1 month, criteria for schizophrenia are not met, and the condition cannot be attributed to other medical or neuropsychiatric conditions.

"Many of these people are very high-functioning. I have corporate CEOs who fly in to see me in their private jets. At work, they're king of their domain. At home, their family is falling apart because of their delusion," said Dirk M. Elston, MD, professor and chair of the department of dermatology and dermatologic surgery at the Medical University of South Carolina, Charleston.

"These people suffer, and the people around them suffer," he emphasized.

Dozens of medical conditions can cause intractable itching or biting sensations. Far and away at the top of the medical differential diagnosis is thyroid disease, given its high incidence and frequent presentation with anxiety and itch. Other possibilities that can readily be ruled out via lab tests include substance use – especially involving amphetamine/methamphetamine, cocaine, or opioids – liver or kidney disease, diabetes and other sources of peripheral neuropathy, polycythemia, dermatitis herpetiformis, and pemphigus, Elston said.

Dr Scott Norton

Scott A. Norton, MD, MPH, MSc, a dermatologist and preventive medicine specialist at the Uniformed Services University of the Health Sciences in Bethesda, Md., noted that a diagnosis of DI requires three elements: The presence of abnormal sensations in the skin, a patient's tenacious conviction that the sensations are caused by an infestation, and a lack of supporting evidence for that conviction.

Taking an accurate medical history can be a challenge in these patients because they are often so guarded. They won't disclose that they've already seen other health care providers, or that they've been self-treating with OTC veterinary medicine products, such as high-dose topical or oral ivermectin. They'll often even deny repeated scratching despite clear evidence to the contrary from the skin exam.

As a dermatologist, Norton considers his first task to be a search for evidence of an infestation. Scabies is usually the first diagnosis proposed to account for the uncomfortable skin sensations. The presentation can be subtle. While the classic teaching is that the telltale signs of infestation by Sarcoptes scabiei are burrows in the skin and a rash in the web spaces between the fingers, he finds these features are often absent or equivocal.

"I think there are two more reliable presentations of scabies: Check to see if there's symmetric involvement of the volar or palm side of the wrists; if there isn't, I'm skeptical of the diagnosis. And every male older than 1 year of age with scabies will have scabies nodules on their genitalia. If the penis, the glans, or the scrotum aren't involved with the nodules, I discard scabies as a possible diagnosis and look for evidence of other skin conditions that can plausibly explain the sensations and skin lesions, like eczema, contact dermatitis, scalp folliculitis, or dry skin," he said.

If he can't find evidence of infestation, he next systematically looks for another dermatologic cause of the patient's sensations. When that proves fruitless, he tries to determine if there might be a biomedical or neuropsychiatric cause, such as depression, anxiety, schizophrenia, or dementia.

Taking a personal hygiene history is helpful. Patients who believe they have an infestation may bathe or shower three to five times daily with harsh soaps, causing dry, inflamed, itchy and uncomfortable skin.

"Many patients are thrilled to hear the good news that the history, physical examination, and lab tests do not show an infestation and that we have another explanation to account for their unwanted sensations. However, there are some patients who vehemently reject that idea and immediately return to their unwavering, unalterable belief that they are in fact infested. At this point, the possible diagnosis of DI looms large," the dermatologist said.

Clues suggestive of DI include a patient's obsessive focus on collecting "specimens" of the offending pathogen in Ziplock bags for assessment during the office visit – "usually a mix of unhelpful household debris and environmental detritus" – and eager presentation of a lengthy and detailed infestation diary, Norton said.

"Among the most distinctive signs that the patient is detached from reality are the biologically implausible descriptions and explanations of the supposed attacking organism. It's a fanciful amalgamation of mutable features, behaviors, and life cycles composed of a composite of taxonomically unrelated organisms – for example, fungal hyphae with wings – that shapeshift at will to evade detection," he said.

Elston observed that DI skin lesions are typically excoriated, sometimes because of a patient's systematic use of a sharp object in an effort to dig out the infestation.

"One of the clues is the angularity of the lesion," the dermatologist noted. "We always say round-to-oval lesions suggest an inside job; angulated lesions suggest an outside job, like fingernail work. There's often a row of good healing border showing there's really nothing wrong with wound healing, but a fibrinoid base where the excoriations have occurred. And the lesions are often in various stages of healing."

Don't forget neuropathic itch in nondelusional individuals as a potential cause of sensations of infestation and self-injury due to relentless scratching, urged Anne Louise Oaklander, MD, PhD, associate professor of neurology, Harvard Medical School, Boston, who is director of the nerve unit and the neurodiagnostic skin biopsy lab at Massachusetts General Hospital, Boston.

"There's no one cause of patients' impressions that they may have insects. Let's be sympathetic: It is a normal assumption that insects may be present if the skin itches. One problem is that when patients don't get good medical diagnoses they make up their own explanations, and sometimes these include persistent ideas of infestation. Many of them don't realize that their scratching is a cause, not a result, of their skin lesions," said Oaklander, who has conducted pioneering research on unintentional self-injury due to neuropathic itch accompanied by loss of pain signaling.

"Rapport First, Medication Later"

"The office visits are typically difficult to conclude, but skills can be learned and make it much easier to help these people," Elston said.

John Koo, MD, emphasized that establishing rapport is "by far" the most important part of managing patients with DI.

"Rapport first, medication later. This may require multiple visits," said Koo, professor of dermatology at the University of California, San Francisco, who is a board-certified psychiatrist.

He makes sure he walks into the examination room all smiles and positivity. Patients with DI are eager to expound on their ailment; he lets them talk for a while, then when the timing is right, he actively encourages them to shift their focus away from etiology to treatment.

Koo and coworkers have described a spectrum of mental fixation in DI ranging from having only crawling and biting sensations, progressing to holding an overvalued idea as to their cause, then on to DSM-5 somatic preoccupation, followed by becoming truly delusional, and finally terminal delusion, where the patient doesn't care about getting better, but only wants the physician to agree there is an infestation (J Clin Exp Dermatol Res. 2014 Oct. 3. doi: 10.4172/2155-9554.1000241).

"You cannot argue with people with delusions. How you talk to them as a clinician depends on whether they are entirely delusional or not," he advised. "I cannot agree with their ideation, but I can agree with their misery – and that's how I make a connection."

Declining a DI patient's request for a skin biopsy when it's obvious there is no infestation can lead to a counterproductive power struggle. Instead, Koo turns the patient request into an opportunity to form a verbal contract: "I ask, 'If the result comes back negative, can you be open-minded about the possibility of other etiologies besides parasites?' "

As for Norton, when his schedule shows a patient is coming in for a first visit for a supposed skin infestation, he tells his staff to expect a lengthy session as he works at establishing a good relationship.

"When my patients arrive with bags of specimens, I ask them to select two or three that they're most confident will have a creature in them. Then I bring a two-headed microscope into the exam room and ask the patient to join me in examining the material. It helps with rapport by showing that I genuinely want to determine if there's an infestation," he explained.

He then sends the specimens to a laboratory, which provides a full report of the findings.

In performing a skin biopsy in a patient with suspected DI, Norton routinely biopsies two sites so the patient can't claim sampling error when the pathology report comes back with no pathogens or parasites found. Also, he asks the patient to choose biopsy sites with intact skin where he or she believes the infestation exists. There is no point in biopsying excoriated lesions because they often contain snagged textile fibers.

Another rapport-building strategy: "I try to design a treatment regimen that will palliate the uncomfortable sensations and help relieve the patient's misery while we continue working towards treating those delusions," Norton said.

This might entail cutting back to one lukewarm shower per day with gentle or no soap, coupled with moisturizing, oral antihistamines or doxepin for itch, topical corticosteroids for the associated inflammation, and oral or topical antibiotics for any secondary bacterial skin infection.

What he doesn't recommend as a rapport-building strategy or simply in order to get the patient out of the office is offering a therapeutic trial of an antiparasitic agent. That's counterproductive. It may reinforce the false belief of infestation, and when the medication doesn't bring lasting belief, the patient may conclude the infestation is resistant to conventional treatment.

Koo tells affected patients that he suspects they have Morgellons syndrome. He doesn't call it DI in their presence.

"These people would not like their condition to be called delusional," he explained. "Morgellons is a more neutral term. I tell them it's a mysterious condition, and that what I'm really interested in is in trying to get them out of their misery."

Treatment Tips

Koo's first-line medication for DI is pimozide (Orap), which in the United States has the advantage of being approved only for Tourette syndrome; it's an antipsychotic without the perceived stigma of a psychiatric indication.

"Many of these patients will not consider taking any medication that has any psychiatric indication," he noted.

Low-dose pimozide is highly effective, according to Koo, who recommends starting at 0.5 mg to 1 mg/day, increasing by 0.5 mg/day every 2-4 weeks. The drug is usually effective at a dose of 3 mg/day or less. Once a patient's symptoms become clear or almost clear, the patient is maintained on that dose for another 3-4 months, then tapered by 0.5 mg/day every 2-4 weeks.

"In 35 years of seeing a new patient on average every week or two, I've had only five patients with one recurrence and one patient with two recurrences. All six responded to repeat therapy," Koo said.

Side effects at these low doses are "very rare," he added. Diphenhydramine (Benadryl) at 25 mg up to four times daily is effective for complaints of stiffness or restlessness. Prolongation of the QT interval is a potential concern, but Koo has never encountered it despite routinely ordering ECGs for patients on pimozide with known heart disease or who are over age 50.

When a patient can't tolerate pimozide, Koo's second-line antipsychotic for DI is low-dose risperidone (Risperdal), which is also highly effective.

Lepping noted that the European situation is different. There, unlike in the United States, pimozide has regulatory approval as an antipsychotic, so it loses the advantage of being an under-the-radar neuroleptic. His go-to medication is the first-generation antipsychotic sulpiride (Dogmatil), which he finds has a more favorable side effect profile than pimozide, particularly in the elderly. (Sulpiride is not approved in the United States.)

In treating DI, he prefers more dopaminergic-focused antipsychotics over those covering a broader spectrum of receptors. His alternatives to sulpiride include risperidone and olanzapine, atypical antipsychotics. He explains to patients that just as aspirin is used in low doses for its antiplatelet effect and in higher doses for pain relief, these medications can help them feel better at much lower doses than for schizophrenia.

"Once we get some rapport and a trusting relationship going, we normally try to persuade people to basically try something against their better judgment. We know that they don't believe in it, but you try to get them to at least try something because everything else has failed," Lepping explained. "We tell them it's a condition we have seen before, and we have seen these medications to be useful because they are good for their distress, they help with making them calmer, and they might help with their symptoms. We say, 'What do you have to lose if you trust us?'

"About 60% of our patients take the medication and almost invariably they all get better," the psychiatrist said. "The others we either lose to follow-up or they just refuse to take the medication."

A patient's first visit to the Liverpool multispecialty DI referral clinic is 1 hour long. "They know that in advance, and we very much stick to that hour. We say to people up front, 'We have an hour – that's a lot, but we don't have more,' " he said.

The initial visit is typically followed by two to four 30-minute follow-up visits. Lepping recommends that when possible, patients with DI should be seen jointly by a psychiatrist and a nonpsychiatrist physician. He finds this approach leads to substantially better clinical outcomes than with a single health care provider.

"If you have two people in the clinic with the patient, when you get really annoyed and your amygdala really starts going, that's the time when you can then turn to your colleague and say, 'Oh yes, and Professor Squire, what do you have to say to that?' So as you see the red mist rising in yourself because you're getting so exasperated, you have the other person there to take over so you can calm down. And then the other person does the same. That can be really important to deescalate a heated situation," Lepping explained.

Roughly 10% of patients with DI have what is termed folie à deux, where the delusion of infestation is shared by another person.

Dr Jason Reichenberg

"Anecdotally, I would say those are much more difficult to treat," said Jason S. Reichenberg, MD, MBA, professor of medicine (dermatology) at the University of Texas at Austin and president of the Ascension Medical Group Texas.

"It's like getting somebody to quit smoking when everybody else in the house is still smoking. It's very hard to convince a single family member that they're wrong when everybody else in their family keeps telling them they're right," he said.

Recent Advances in DI Research

Lepping and coinvestigators at multispecialist DI clinics in London, Italy, and Moscow reported in an unusually large observational study of 236 affected patients that longer duration of untreated psychosis was associated with significantly worse clinical outcome. It's a finding consistent with Koo's construct of progressive stages of delusionality, and it underscores the need for early treatment.

"Having said that, improvement is still possible, even if people have had quite a long time of untreated psychosis," Lepping said. The same study also showed that older age at illness onset was inversely associated with good outcome.

In another study, Lepping and colleagues reported that substance use involving amphetamines, cocaine, opioids, and other drugs that can cause itch was roughly twice as common in a group of patients with DI compared to the general population. "I highly recommend, if at all possible, a drug screen in suspected DI," he said.

In a large survey of U.S. and Canadian veterinarians, Lepping and coinvestigators found that these practitioners not infrequently encountered delusional infestation among pet owners who claimed their dog or cat is infested when it's not. This is called "delusion by proxy," and it often leads to unwarranted animal euthanasia. Some of these pet owners claim they, too, are infested, which the investigators termed "double delusional infestation."

MRI Studies

Recent structural brain MRI studies support the concept that impaired somatosensory neural networks mediate the delusional symptoms of DI, but not in delusional disorders without somatic content. This was demonstrated in an MRI study by Lepping and others conducted in 18 patients with DI, 19 others with nonsomatic delusional disorders centered on themes of persecution or jealousy, and 20 healthy volunteers. The DI group had lower gray matter volume in prefrontal, thalamic, striatal, and insular regions of the brain compared to the other two groups.

Of note, mapping of the insula and dorsal striatum indicates they are part of the peripersonal space network, which integrates tactile and visual perceptions involving the area near the body surface. The insula also mediates feelings of pain and disgust.

Some of the same investigators have also recently reported brain MRI evidence specifically of cerebellar dysfunction in patients with DI, who displayed decreased gray matter volume in left lobule VIIa of the cerebellum and increased gray matter volume in bilateral lobule VIIa/crus II compared to patients with non-somatic delusions. This points to a role for impaired cerebellar neural networks related to somatosensory perception in patients with DI but not in those with non-somatic delusions.

Delusional Infestation: What's in a Name?

Ekbom syndrome. Delusional parasitosis. Morgellons syndrome. These and other terms are increasingly giving way to 'delusional infestation' as the preferred moniker for the disorder. That's in part because the delusional focus in patients with this condition has shifted over time. In the 19th century, for example, affected patients often attributed their infestation to typhus.

In contemporary practice, roughly one-quarter of affected patients think they are infested by small inanimate objects, most commonly fibers or threads emerging from the skin, rather than by parasites, insects, or worms. In a study of 148 consecutive European patients with suspected DI, Lepping and coinvestigators reported only 35% believed they were infested by parasites.

"The name 'delusional infestation' emphasizes the constantly changing pathogens and covers all present and future variations of the theme that are bound to occur," Lepping observed.

All speakers reported having no conflicts of interest.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.

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