Contributor: Taylor Lynch, MD

Educational Pearls:

• Delusional parasitosis is a subtype of the psychiatric condition delusional disorder
  • Defined as a fixed, false belief of infestation by parasites or other organisms
  • A somatic type of delusional disorder
• Primary delusional parasitosis
  • Occurs in the absence of other psychiatric or medical conditions
• Secondary delusional parasitosis
  • Causes include methamphetamine use disorder, schizophrenia, neurologic diseases, or medical conditions such as thyroid disease
• Pathophysiology
  • Poorly understood
  • Upregulation of striatal dopamine system is implicated
• Management
  • Form a strong therapeutic alliance and do not discredit the patient immediately
  • Perform a full physical exam
    • This helps reassure the patient and strengthen the therapeutic alliance
    • Some day there may be a patient in whom this is not a delusion
• Treatment & Management
  • Discontinuation of substances if substance-induced
  • Antipsychotic medications like risperidone or olanzapine

References

1. Lepping P, Russell I, Freudenmann RW. Antipsychotic treatment of primary delusional parasitosis: systematic review. Br J Psychiatry. 2007;191:198-205. doi:10.1192/bjp.bp.106.029660
2. Moriarty N, Alam M, Kalus A, O'Connor K. Current Understanding and Approach to Delusional Infestation. Am J Med. 2019;132(12):1401-1409. doi:10.1016/j.amjmed.2019.06.017
3. Skelton M, Khokhar WA, Thacker SP. Treatments for delusional disorder. Cochrane Database Syst Rev. 2015;2015(5):CD009785. Published 2015 May 22. doi:10.1002/14651858.CD009785.pub2

Summarized and Edited by Jorge Chalit, OMS4

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