By Gary M. White, MD
This man thought bugs were in his skin so he had to get them out.
Delusions of parasitosis (DOP) is a rare psychiatric disorder in which the patient falsely believes that his or her skin is infested with parasites. Even though it is a psychiatric disorder, these patients usually present to a dermatologist because they are convinced that they have a dermatological problem. Patients with delusions of parasitosis generally reject psychiatric referral. The patient may go in and out of a delusional state. (A delusion is a false idea that the patient holds to firmly and cannot in any way be convinced of otherwise. A patient who will honestly consider the possibility that they do not have bugs is not strictly delusional.) It may arise as a primary condition or secondary to a variety of disorders including drug use (e.g. alcohol, cocaine or amphetamines), organic brain dysfunction, or schizophrenia. A toxicology screen may be needed. One case is reported of DOP secondary to severe iron deficiency anemia [JAAD Case Reports 2017; 3;390–391].
By definition, there is no evidence of scabies, lice, any other infestation or primary lesion. There is often much excoriation. Large ulcers may be created. The patient may bring in various plastic bags or containers with various hairs, flakes, crust and other material for the dermatologist to examine.
Some patients will present with the same clinical picture as DOP, but instead of believing the skin contain bugs, they will have delusions of "thorns" or "splinters" or "shards of glass". One patient of mine dropped a mayonnaise jar in the kitchen which shattered. For years thereafter, she insisted shards of glass were buried throughout her skin and she had to dig them out.
It is always preferable to have the patient see a psychiatrist, but this is usually rejected by the patient. "I'm not crazy!" Thus, the dermatologist is faced with the dilemma of whether or not to treat using psychiatric medication with which s/he may be relatively unfamiliar.
What is more ethical to tell the patient?
For an excellent discussion of these issues, see [J Am Acad Dermatol. 2013 Jul;69(1):156-9].
This author has healed large ulcerations by providing close followup focusing on wound care and dressings. For example, seeing a patient weekly, praising for any progress in healing, encouraging covering any ulcerations or problematic areas and trying various topical therapies (e.g., lotions, Vaseline, bandages, topical steroids, etc.) can greatly benefit the patient. The trouble of course comes when this close observation comes to an end. Relapse is unfortunately likely.
Rapport may be engendered by faithfully examining any material brought in by the patient as proof. Usually this involves using the microscope. In most cases, the material is dried serum, crust, keratin and/or clothing fibers. The physician should always have an open mind however as rarely, ants, bird mites or other insects may be found.
Sometimes the patient will insist that the bug(s) is/are in a certain part of the skin and biopsy can be helpful. It is usually best to have the patient identify the exact spot to be biopsied so as not to have the patient later say, "you just didn't biopsy the right spot".
Consultation with a psychiatrist is recommended for prescribing any of these medications unless the physician is familiar with their use. The patient may be told, "I am not sure how this medication works, but it has helped other patients." Pimozide is often used.
Risperidone has been recommended as being both effective and safer than pimozide [JAAD 2000;43;683].
One of my patients with DOP had his hemoglobin drop from the 15s to the 12s. When asked about it, he admitted to a significant bleed while he was "treating his skin". He said, "there was blood everywhere."
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