Dr. John Koo discusses a practical approach to diagnosing, treating, and managing patients who present with delusional parasitosis.
John Koo, MD, Board Certified in Dermatology and Psychiatry, Professor, University of California San Francisco Medical Center, Department of Dermatology, Co-Director of Psoriasis Skin and Treatment Center.
“I made my presentation as understandable as possible for [a] nonpsychiatric audience. The main topic was how to handle somebody with delusional parasitosis,” said John Koo, MD, who presented “Practical Psychodermatology” at this year’s Pacific Derm meeting.
“Delusional parasitosis, every dermatologist knows, is a condition where a patient shows up with a complaint and conviction that they are infested by parasites, when in fact they’re not infested by anything.”
According to Dr. Koo, these patients often feel crawling, biting, and/or stinging sensations.
“The problem with this situation is that dermatologists are never trained in terms of how to relate to and connect with a psychotic patient.”
Typically, dermatologists are truthful with patients and let them know what they do or don’t have, said Dr. Koo. But this approach can backfire with patients suffering from delusional parasitosis.
“You have to be very careful about what you say in front of the patient and what you write in your notes. If you write that the patient is psychotic, delusional, [and/or] hallucinating, the patient can access the notes. Then you can really have trouble on your hands: angry patients who might complain to the medical board and threaten your licensure or who might sometimes even bring a malpractice suit.”
The solution lies in careful documentation, said Dr. Koo. Write down the patient’s chief complaints using their words.
“Especially the more bizarre part of the complaint. You know, like, I have 1000 insects crawling all over me; they’re eating me alive. These insects have 10 antennas and 18 legs and 5 eyes… The more bizarre it is, the better, and then you put that in quotes.”
Not only will this demonstrate the patient’s delusional status but also make the patient happy by showing them that you are paying attention to the details, he said.
Whatever you do, don’t use the phrase “delusional parasitosis” to describe their condition, said Dr. Koo.
“Because they often feel crawling and biting stinging sensations, I put down ‘cutaneous dysesthesia’. Cutaneous means skin; dysesthesia means disagreeable sensations. And that’s just a descriptive, accurate diagnosis.”
When patients bring in specimens for diagnosis, Dr. Koo shifts some of the work to the patients themselves.
“I make it easier for myself because in the middle of busy practice, if somebody brings in bottles and bottles of dirty water with something floating in [them], I don’t have time to tease out these things then look under the microscope.”
Instead, he thanks the patient for collecting specimens and explains that the best way to examine their samples is using a microscope.
“I actually give them glass slides. Not too many, maybe five or six at most.”
He tells patients to choose the most relevant specimens and to use clear packing tape rather than Scotch tape to secure specimens to the slides because the matted surface of Scotch tape ruins the specimen.
“And I’m amazed how they prepare slides so beautifully… And then, of course, I look at it and, of course, I don’t see any parasite or insect. But this way, I can actually save time and at the same time make the patient happy.”
A Practical Approach
There are several steps to employing a practical approach to effectively treating patients with delusional parasitosis, said Dr. Koo. First, don’t offend and, second, establish rapport.
“Connecting with delusional patients means that you let the patient dictate how things go within reason… when you have delusional patients, you have to revolve around them until [you] have good rapport.”
According to Dr. Koo, the conversation about anti-psychotic medication doesn’t happen until that rapport is established. And this is where the next practical piece of advice comes in: Don’t call their medication an anti-psychotic.
“If I say this is anti-psychotic, obviously they’re not going to take it.”
Pimozide (Orap) is an FDA-approved medication for Tourette’s syndrome and not US-FDA indicated as an anti-psychotic, said Dr. Koo.
“This medication turned out to be so much more acceptable for delusional patients than any other… [that is] officially labeled as anti-psychotic.”
According to Dr. Koo, deliberately telling patients that pimozide is an anti-Tourette’s helps to put them at ease.
“In fact, I proactively, explicitly advertise that this is a medicine that is not a psychiatric medication, but it can help your problem.”
After establishing a good rapport, many patients are willing to try these medications, said Dr. Koo.
“And the good news is, the medications we have available, with names like pimozide, and then some psychiatric medications like Risperdal or Abilify, they really work well. It’s pretty amazing how well they work.”
But patients also often want to find the offending parasite, said Dr. Koo, so he refers to their condition of delusional parasitosis as a “mysterious” phenomena or to Morgellons disease if they insist on a named diagnosis.
Morgellons disease is similar to delusional parasitosis but doesn’t sound as bad to patients as delusional parasitosis, he said.
No matter what you call it, the important thing is getting patients onto treatment because treatment works, said Dr. Koo.
However, results aren’t immediate.
“I slowly go up on the dose for pimozide or Risperdal: half-a-tablet increment every two to three weeks until we hit the effective dose, which is usually about 3 mg per day.”
Patients remain at that dose until their symptoms almost or completely disappear, said Dr. Koo.
“Once we get to that point, I tell the patient ‘don’t stop the medicine’. We go for another three or four months because if you stop that earlier, they may experience recurrence, which can be very discouraging to the patient.”
This titration approach almost always cures, said Dr. Koo. For the few patients who may recur, simply repeat the treatment.
“So that’s the practical way. Number 1: Within reason, you have to revolve around the patient because you don’t want to offend the patient. Number 2: You have to focus on having positive rapport and not think about medication first—rapport first; medication second. Number 3: Introduce the medication not as anti-psychotic, but as a trial-and-error way to get out of this ‘living hell’. 4. Once the medication starts to work, do not be too anxious to discontinue it; take your time and go for the cure.”
