Journal of Dermatology for Physician Assistants

The official journal of the Society of Dermatology Physician Assistants

#06-Demodex Mites in Patients with Non-melanoma Skin Cancer

SDPA Presents 20th Annual Fall Dermatology Conference–Abstracts and Posters

November 16-20, 2022, Miami, FL

Claire Gist Bradberry B.A.1, Samantha Robinson Ph. D.2, Hanna Jensen M.D.3, and Chris Schach M.D.1,4

From the: 1College of Medicine, University of Arkansas for Medical Sciences, Northwest Regional Campus, Fayetteville AR; 2Department of Mathematical Sciences, University of Arkansas, Fayetteville, AR; 3Department of Surgery, University of Arkansas for Medical Sciences, Northwest Regional Campus, Fayetteville, AR; 4Ozark Dermatology Clinic, Fayetteville, AR

Click here to download poster

Background: Demodex mites are human ectoparasites that reside in hair follicles. A density of >5 mites/cm2, called demodicosis, is considered pathologic,1 and has been associated with immunosuppression.2 The purpose of this study was to determine if there was an association between Demodex mite density and patients who had non-melanoma skin cancer (NMSC). The NMSC patients studied had no history of demodicosis or demodex related disease process.

Methods: This study was a retrospective review of patients with a history of NMSC at a single dermatology clinic from 06/2022 to 07/2022. Each patient’s medical record was queried for documentation of a history of NMSC, and the density of mites on 1 cm2 of skin at the right or left suprabrow which were measured by standardized skin surface biopsy (SSSB) with direct microscopic examination (DME). A t-test was used to determine if the mean density of mites/cm2 in the NMSC patient population exceeded 5 mites/cm2, which is the average density among healthy adult populations.

Results: A total of 27 patients were included in the study. The average age was 74 years, 48% were female, and all had a history of NMSC. Results indicated that the NMSC patient population studied has a significantly higher density than 5 mites/cm2 (M = 21.78, SD = 34.86, t(26) = 2.50, p = .0095, Cohen’s D = 0.48), with the Cohen’s D effect size indicating a medium effect. At the 95% confidence level, the mean density of the diseased population is estimated to be between 7.99 and 35.57 mites/cm2. A 95% confidence interval was constructed to estimate the overall incidence of demodicosis in the diseased population. Results indicated that between 39.01% and 76.99% of this population exhibit demodicosis.

Conclusions: The team’s findings indicate that there were associations between an increased density of mites and history of NMSC. Patients with NMSC had a significantly higher density than 5 mites/cm2 and a rate of demodicosis between 39.01% and 76.99%. These findings may help health care providers in screening patients who are at high-risk for developing non-melanoma skin cancer. Future research is needed to determine why NMSC patients have a higher prevalence of demodicosis and which came first: the mite or the immunosuppression.


[1] Perandones González H, et al. Ex vivo dermoscopy in demodicosis, Journal of the American Academy of Dermatology. 2021;ISSN 0190-9622.
[2] Rather PA, Hassan I. Human demodex mite: the versatile mite of dermatological importance. Indian J Dermatol. 2014;59(1):60-6.

Like this article?

Share on Facebook
Share on Twitter
Share on Linkdin