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Child Psychiatrist /Adult Psychiatrist

Phased Approach Recommended for Patients With Delusional Infestation

SAN DIEGO — In the clinical opinion of Jenny E. Murase, MD, caring for patients with delusional infestation — the conviction that one is infested by animate or inanimate pathogens without medical or microbiological evidence of a true infestation — puts a dermatologist's communication skills to the ultimate test.

Delusional Infestation

"The fact that delusional infestation is a fixed, false belief [means] we will never agree with patients on the etiology by definition," Dr Murase, a dermatologist with the Palo Alto Foundation Medical Group, Mountain View, California, said at the annual meeting of the American Academy of Dermatology. "But somehow, we must come to some kind of an agreement on how to approach this therapeutically."

Patients with delusional infestation (DI) often describe a cutaneous sensation of itching or crawling, biting, stinging — a pins and needles sensation. "Formication is when there's a crawling sensation on the surface of the skin," she said. "That's something we can agree on — the fact that there is a shared understanding that they're experiencing some kind of sensation in their skin."

First described in 1894, several different terms have been used to describe DI in the past, including acarophobia, delusions of parasitosis, Ekbom syndrome, and Morgellons disease. The current term used for DI includes other animate or inanimate pathogens besides parasites.

The average dermatologist manages two to three patients with DI every 5 years, "so it's not uncommon," said Dr Murase, who also holds a faculty position in the department of dermatology at the University of California, San Francisco. Females are about 2.5 times more likely to be affected compared with males, she said, and 8%-12% of patients with DI have a friend or relative who shares the symptom, and they often accompany them to the office visit. "Initially, you're trying to determine if this a primary condition where it's only the cutaneous condition the patient is experiencing, or if there is a secondary condition like an underlying psychiatric disorder or medical condition or drug use that contributes to the sensation," she said.

According to a descriptive study of 115 patients with DI, 50% had at least one drug detected in hair samples, and nearly 60% had evidence of some cognitive impairment that could not be explained by deficits in IQ. Another study of 147 patients with DI seen at the Mayo Clinic between 2001 and 2007 found that 81% had a prior psychiatric condition and 26% had a shared psychotic disorder.

Phased Approach to Treatment

Dr Murase discussed her phased approach to caring for patients with DI, based on a review article that she and colleagues published in the International Journal of Dermatology. Phase 1 involves preparing for the visit by asking staff to refer to patients with DI as VIPs and allowing them to talk freely about the sensation they're experiencing. "The goal is to improve the patient's condition, not to convince the patient that he or she is delusional," Dr Murase explained. "Many patients can't distinguish between when they're talking to the doctor and when they're talking to a nurse or a nurse practitioner; they like to feel that they're being heard and listened to."

She also recommends scheduling patients with DI for the end of the day and arranging frequent follow-up visits. "Making them feel valued is the bottom line," she emphasized. "Remember: They're less likely to respect socially defined boundaries like time constraints, so you do have to set boundaries, and don't take what they may say to you personally. You're not going to be able to care for that individual unless you do that. They may appear defiant, frustrated, and angry, but the fact that they showed up in your office means that you can help that person."

Phase 2 of care for these patients consists of building a therapeutic rapport by greeting them with a smile and positive attitude and using welcoming body language such as sitting side-by-side during the office visit as opposed to face-to-face, "so it's a less aggressive approach," she said. Next, ask about their goal with a question such as, "Is it more important for you to find the bug/virus or to improve your condition?"

During the visit, "you're continually shifting from etiology — which they are desperate to understand — to a shared desire for treatment," Dr Murase said. "No one knows what causes DI and remember, in medicine we treat patients when the exact etiology is unknown. So, we're not doing anything that differently. Focus on the effect that the symptoms are having on their life. Say something like, 'it must be so miserable to be living this way. I really want to help you.' "

Phase 3 of care for patients with DI involves performing a thorough history and physical exam. The initial office visit should include a full body exam to rule out any underlying dermatologic condition that may be causing the sensation they're complaining about. She cited a retrospective study of 108 patients who presented to the Mayo Clinic with DI as the main reason for their office visit. Of the 80 patients who had a biopsy, 61% had chronic dermatitis; 48% had excoriation, ulceration, or erosion; and 31% had nonspecific dermal inflammation.

Whether to perform a biopsy or not is controversial, Dr Murase added, because it's probably not going to change the clinical impression or diagnosis. "If you agree to do the biopsy, get a verbal contract with the patient," she advised. "You might say, 'We're going to do this. You're going to choose the site, we're going to do a biopsy, but we are going to be in agreement here that, if we can't find the etiology, that you will still be open to going on therapy.' This is important because it establishes a therapeutic alliance."

Since patients with DI often bring in their own specimens, she also recommends providing them with microscope glass slides without cover slips and asking them to use clear tape, not tape that is opaque or matted, to cover the specimen.

To rule out other illnesses and conditions that could be triggering the perceived DI, she said lab tests to consider include a complete blood count, comprehensive metabolic panel, thyroid-stimulating hormone, calcium, hemoglobin A1c, vitamin B12, urinalysis, toxicology screen, HIV/hepatitis C, and rapid plasma reagin.

Starting Treatment

Phase 4 of care for patients with DI involves initiating therapy, which includes demonstrating empathy by reflecting on the detrimental effects of the patient's reported sensations on their quality of life. "Emphasize that you are not questioning their experience, and that you don't doubt that they feel things on their skin," Dr Murase said. "Recommend medications on an empirical or 'trial and error' pragmatic basis. I often tell patients, 'I will never give up on you if you will never give up on me.'"

For treating patients with DI, her first-generation antipsychotic of choice is pimozide. She starts at a dose of 0.5 mg, building up to 2-3 mg once a day. Haloperidol is another option: 0.5 mg to start, building up to 1-5 mg every night at bedtime. "This requires monitoring for bone suppression via CBC and hypermetabolic complications via fasting lipids and HbA1c," she said. "There is also an increased risk of prolonged QT with pimozide and risk of extrapyramidal symptoms and tardive dyskinesia."

Second-generation antipsychotics to consider include risperidone (0.5 mg to start, building up to 102 mg at bedtime); olanzapine (2.5 mg to start, building up to 5-10 mg at bedtime); aripiprazole (2-5 mg to start, build ing up to 10-15 mg a day), and quetiapine (12.5 mg to start, building up to 200 mg at bedtime).

For all medical therapy she recommends starting patients with a low dose, increasing by 0.5 mg every 2-3 weeks, and let them be "stable and comfortable" for 3-4 months, and then taper down the dose by 0.5 mg every 2-4 weeks or more slowly. In the medical chart, Dr Murase recommends avoiding use of the terms "psychosis" and "delusions." Instead, "formication" (tactile hallucination of insects crawling on or within the skin) or "cutaneous dysesthesia" are better terms if patients access their records, she said.

Note: This article originally appeared on, part of the Medscape Professional Network.

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