Delusions of Parasitosis Workup

Updated: Sep 29, 2023
  • Author: Bettina E Bernstein, DO, DFAACAP, DFAPA; Chief Editor: Glen L Xiong, MD  more...
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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.


Imaging Studies

Huber et al found striatal lesions in patients with secondary delusions of parasitosis, but not in cases of primary delusions of parasitosis. [38] 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.


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 biopsies on them is not useful because any finding, even if negative for parasites, will not affect the delusion. [39]