Innov Clin Neurosci. 2025;22(7–9):40–41.

by Adil Tumbi, MD; Amit Mistry, MD; BreAnna-Anh Le, BS; and Steven Lippmann, MD

Drs. Tumbi and Mistry are with the Oklahoma City Veteran Affairs Health Care System in Oklahoma City, Oklahoma. Ms. Le is with University of Oklahoma College of Medicine in Oklahoma City, Oklahoma. Dr. Lippmann is with University of Louisville School of Medicine in Louisville, Kentucky.

FUNDING: No funding was provided for this article.

DISCLOSURES: The authors declare no conflicts of interest relevant to the content of this article.

Delusional parasitosis is a psychiatric disorder in which one experiences a persistent, false belief of being infected by parasites or other organisms.^1,2 It is often accompanied by formication, a tactile hallucination perceived as “skin crawling,” with or without pruritus. There is no evidence for primary cutaneous pathology; rather, any skin manifestations are self-inflicted (eg, scratching). As with all medical disorders, one must rule out other potential pathology, such as allergies, nutritional deficiencies, medication-related adverse events, infections, and/or malignancies.³ The quality of the patient-physician relationship can help to predict prognosis, especially because patients with this condition may be less well-treated.^1,2

Case Presentation

A 45-year-old male patient presented with persistent pruritis and formication, which he believed to be caused by “bugs.” His past medical history included Crohn’s disease, opioid use disorder, and post-traumatic stress disorder. For the past two years, he had received regularly scheduled infliximab infusions and remained stable on buprenorphine and mirtazapine. His primary care physician twice prescribed permethrin cream and ivermectin, considering a scabies diagnosis. The patient’s condition did not improve, so he was referred to a dermatologist. After that evaluation, the diagnosis was changed to delusional parasitosis. Despite being shown the validity of that diagnosis, the patient still insisted that he was bug-infested and continued to received permethrin cream, along with multiple emergency department assessments. He was prescribed pimozide but was nonadherent. Subsequently, he consulted other physicians in neurology, gastroenterology, hematology, and general surgery, with each one ruling out specific differentials. Once, the presence of red skin nodules were noted, which indicated an antibiotic drug intervention, together with ongoing permethrin in the midst of clinical course. A psychiatrist eventually prescribed alprazolam to treat the patient’s anxiety and built a strong patient relationship. That allowed pimozide to be prescribed. Both the antibiotic and pimozide were prescribed after the patient was seen by dermatology, but he did not start taking pimozide until after he began taking alprazolam. The pimozide diminished the pruritis when it became a clinical concern; nevertheless, while less anxious the patient still believed that he had “bugs.” Approximately one to two months after starting pimozide, the patient maintained this delusion despite partial symptom relief.

Discussion

Diagnosing and treating delusional parasitosis is difficult. The patient in this index case insisted he was infested with “bugs” despite dermatological evaluation. Diagnostically, scabies and scabies incognito were initially considered, and permethrin and ivermectin were prescribed.³ The duration of permethrin application can potentially exacerbate pruritis,⁴ which appeared to have compromised his recovery. No infections were documented, and there was no suspicion for an allergy causation. The patient then consulted several other physicians seeking confirmation of his belief, which confounded the management of his condition. The prognosis improved after building a rapport with his psychiatrist and with observation of the clinical course. A nutritional deficiency was possible due to the patient’s history of Crohn’s disease, but that was deemed unlikely because the patient took several nutritional supplements, and subsequent testing ruled it out. However, pellagra is established to present similarly to delusional parasitosis.¹ Pruritis can be a nonspecific sign of malignancy.⁵ Regional enteritis also increases the risk for malignancies, such as lymphoma and leukemia, but the clinical signs and laboratory assessments did not confirm such pathology.⁶ Substance abuse and treatment with buprenorphine was another complication. It is well-recognized that undertreated opioid addiction withdrawals can cause tactile hallucinations and formication.² In this case, however, two years of consistently taking buprenorphine and multiple, negative urine drug screen results eliminated drug abuse as an etiologic factor for this condition.

Conclusion

This case illustrates the complexity involved in diagnosing and managing patients with delusional parasitosis. An insistent, fixed nonbizarre delusion of a bug infestation should encourage physicians to broaden the differential diagnoses; hopefully, that yields a wider range of possibilities, testing, procedures, and treatments. This issue highlights the importance of fostering a positive patient-physician relationship and opening communication between physicians in different specialties to help collaborate and provide appropriate care for complicated clinical presentations.

References

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2. Reich A, Kwiatkowska D, Pacan P. (2019). Delusions of parasitosis: an update. Dermatol Ther (Heidelb). 2019;9(4):631–638.
3. Suh KN. Delusional infestation: epidemiology, clinical presentation, assessment, and diagnosis. UpToDate. Updated 4 Jan 2024. Accessed 18 Aug 2024. https://www.uptodate.com/contents/delusional-infestation-epidemiology-clinical-presentation-assessment-and-diagnosis
4. Permethrin: drug information. UpToDate. Accessed 18 Aug 2024. https://www.uptodate.com/contents/permethrin-drug-information
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