Delusions of Parasitosis Workup

  • Author: Noah S Scheinfeld, MD, JD, FAAD; Chief Editor: Dirk M Elston, MD   more...
 
Updated: Jul 18, 2011
 

Laboratory Studies

No laboratory test can help in diagnosing delusions of parasitosis; however, laboratory tests can help identify other diseases that can mimic delusions of parasitosis. Note the following:

  • To exclude infestation, a mineral oil preparation should be used to eliminate scabies, and a microscopic examination of skin and hair should be performed to exclude louse infestation.
  • Neurologic pathology due to toxins or vitamin deficiencies can be evaluated with the appropriate tests.
  • Tests to assess other causes of pruritus (eg, low iron level, liver or kidney disease) can be performed if clinically indicated. Examples include evaluation of the complete blood cell count; urinalysis; liver function tests; thyroid function tests; and determinations of levels of serum electrolytes and glucose, blood urea nitrogen, serum creatinine, serum vitamin B-12, folate, and iron.
  • Unless dermatitis herpetiformis needs to be excluded, skin biopsy is usually more useful to reassure patients of the lack of pathology than to diagnose delusions of parasitosis.
  • Use of cocaine, methylphenidate, or amphetamines must be ascertained, and if occurring, it should be stopped.
  • It is useful to examine the "proof" that the patient brings in so that one may truthfully say that the material was examined and no parasites were found. One authority anecdotally relates how he found ants in the debris and, after explaining that these arthropods did not live on or in humans, was able to give practical advice to reduce the problem.
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Imaging Studies

Huber et al found striatal lesions in patients with secondary delusions of parasitosis, but not in cases of primary delusions of parasitosis.[26] In rare cases, neurologic impairment (eg, tumors, neuritis, multiple sclerosis) can mimic the symptoms of delusions of parasitosis. Causes of such impairment should be excluded with MRI or CT scanning if they are strongly suspected on the basis of the clinical findings.

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Histologic Findings

Delusions of parasitosis have no specific histologic findings. All skin changes are secondary to rubbing, scratching, picking, or other treatment attempts.

Because patients who have delusions of parasitosis are having delusions, performing biospies on them is not useful because any finding, even if negative for parasites, will not affect the delusion.[27]

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Contributor Information and Disclosures
Author

Noah S Scheinfeld, MD, JD, FAAD  Assistant Clinical Professor, Department of Dermatology, Columbia University College of Physicians and Surgeons; Consulting Staff, Department of Dermatology, St Luke's Roosevelt Hospital Center, Beth Israel Medical Center, and New York Eye and Ear Infirmary; Private Practice

Noah S Scheinfeld, MD, JD, FAAD is a member of the following medical societies: American Academy of Dermatology

Disclosure: Optigenex Consulting fee Independent contractor

Specialty Editor Board

Franklin Flowers, MD  Chief, Division of Dermatology, Professor, Department of Medicine and Otolaryngology, Affiliate Associate Professor of Pediatrics and Pathology, University of Florida College of Medicine

Franklin Flowers, MD, is a member of the following medical societies: American College of Mohs Micrographic Surgery and Cutaneous Oncology

Disclosure: Nothing to disclose.

David F Butler, MD  Professor of Dermatology, Texas A&M University College of Medicine; Chair, Department of Dermatology, Director, Dermatology Residency Training Program, Scott and White Clinic, Northside Clinic

David F Butler, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Dermatology, American Medical Association, American Society for Dermatologic Surgery, American Society for MOHS Surgery, Association of Military Dermatologists, and Phi Beta Kappa

Disclosure: Nothing to disclose.

Jeffrey Meffert, MD  Assistant Clinical Professor of Dermatology, University of Texas School of Medicine at San Antonio

Jeffrey Meffert, MD is a member of the following medical societies: American Academy of Dermatology, American Medical Association, Association of Military Dermatologists, and Texas Dermatological Society

Disclosure: Nothing to disclose.

Catherine M Quirk, MD  Clinical Assistant Professor, Department of Dermatology, University of Pennsylvania

Catherine M Quirk, MD is a member of the following medical societies: Alpha Omega Alpha and American Academy of Dermatology

Disclosure: Nothing to disclose.

Chief Editor

Dirk M Elston, MD  Director, Ackerman Academy of Dermatopathology, New York

Dirk M Elston, MD is a member of the following medical societies: American Academy of Dermatology

Disclosure: Nothing to disclose.

References

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