Dermatology: Practical and Conceptual Research Letter | Dermatol Pract Concept. 2024;14(1):e2024044 1 Pigmented Demodex Folliculorum: A Novel Dermoscopic Finding in Brown Facial Macules Magdalena Żychowska1, Linda Tognetti2, Pietro Rubegni2, Elisa Cinotti2 1 Department of Dermatology, Institute of Medical Sciences, Medical College of Rzeszow University, Rzeszow, Poland 2 Dermatology Unit, Department of Medical, Surgical and Neurosciences, University of Siena, Siena, Italy Key words: Demodex, demodicosis, lentigo maligna, pigmented Demodex Citation: Żychowska M, Tognetti L, Rubegni P, Cinotti E. Pigmented Demodex Folliculorum: A Novel Dermoscopic Finding in Brown Facial Macules. Dermatol Pract Concept. 2024;14(1):e2024044. DOI: https://doi.org/10.5826/dpc.1401a44 Accepted: August 17, 2023; Published: January 2024 Copyright: ©2024 Żychowska et al. This is an open-access article distributed under the terms of the Creative Commons Attribution- NonCommercial License (BY-NC-4.0), https://creativecommons.org/licenses/by-nc/4.0/, which permits unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original authors and source are credited. Funding: None. Competing Interests: None. Authorship: All authors have contributed significantly to this publication. Corresponding Author: Magdalena Żychowska, MD, PhD, Department of Dermatology; Szopena 2 Street, 35-055 Rzeszów, Poland. Phone: +48669422237; Fax: 178666294; e-mail: magda.zychowska@gmail.com Introduction The role of Demodex mites in dermatological conditions has not been fully elucidated yet. The mites, at low densities, constitute normal finding in pilosebaceous follicles in adults. However, overproliferation of Demodex, with mites visible to the naked eye as whitish scales at the base of the hair, and accompanied by erythema or subjective complaints (burning, itch, skin hypersensitivity or roughness), is classically defined as demodicosis [1]. Demodicosis may be divided into primary (pityriasis folliculorum) and secondary forms, the latter being associated with rosacea, acne, perioral dermatitis, and bleph- aritis [2]. Recently, a novel entity, pigmented demodicosis (PD), has been highlighted in the literature [3]. Apart from the aforementioned features of demodicosis, PD manifests clini- cally with facial hyperpigmentation and shows under dermos- copy irregularly pigmented circles surrounding hair follicles. The aim of the report is to highlight a new dermoscopic finding, pigmented Demodex, and to outline the differences with the recently described entity, PD. Case Presentation Here, we present five patients with brown facial macules, in whom we observed pigmentation either of the contour or of the whole body of Demodex mites under high magnifi- cation dermoscopy (Horus system, field of view 1.7 mm x 1.275 mm, Figure 1). This case series includes three pa- tients with lentigo maligna (LM), who showed under der- moscopy pigmentation of the Demodex contour (Figure 1, A-C), and one patient with LM, who presented with multiple entirely-pigmented Demodex tails protruding from hair folli- cles (Figure 1, D and E). In two of the aforementioned cases, the presence of pigmented Demodex was not restricted to the heavily pigmented part of LM, but it could be also noted within the areas of regression (Figure 1, C and D). Inter- estingly, we also encountered one patient with solar lentigo, in whom we observed pigmented Demodex as round dark- brown structures inside hair follicles (Figure 1F). Hence, the dermoscopic finding of pigmented Demodex cannot be con- sidered as specific for malignant lesions and it is probably 2 Research Letter | Dermatol Pract Concept. 2024;14(1):e2024044 due to abundant free pigment in the epidermis and/or hair follicles that stains the mites on their surface. Conclusions The presence of Demodex folliculorum is classically con- firmed by standardized skin surface biopsy (SSSB) [2]. Non-invasive imaging methods of use for the detection of Demodex include (video) dermoscopy, reflectance con- focal microscopy (RCM), and optical coherence tomogra- phy [4-6]. Recently, super-high magnification dermoscopy was reported as a valuable tool for non-invasive visualiza- tion of Demodex both inside and outside hair follicles [7]. Whitish gelatinous protrusions from hair follicles, which correspond to Demodex tails, constitute the predominant finding. In addition, grayish dots, scaling, and red dots may be observed. PD is a recently highlighted entity, which clinically pres- ents as facial hyperpigmentation and should be taken into consideration in the differential diagnosis of LM [3]. Under dermoscopy, PD shows irregularly pigmented circles sur- rounding hair follicles, while in RCM dilated follicles with Demodex mites and pigmented keratinocytes around hair follicles may be observed [3]. Differentiation with melano- cytic lesions may be challenging, however, unlike LM, hair follicle obstruction with pigment should not be observed in PD. Histopathological examination of PD reveals interface dermatitis and heavily pigmented melanophages in the papil- lary dermis, presumably corresponding to post- inflammatory hyperpigmentation following Demodex-induced inflamma- tion in dark-skinned patients [3]. We would like to emphasize that the phenomenon ob- served by us, namely presence of pigmented Demodex mites within melanocytic and non-melanocytic facial macules, Figure 1. (A, B) Super-high magnification dermoscopy of lentigo maligna (LM) showing presence of pigmented Demodex as elongated white structures with brown contours (red arrows) inside hair follicle. In addition, non-pigmented Demodex (green arrow) was detected outside the area of the brown facial macule (magnification x150; field of view 1.7mm); (C) LM involving the hairy scalp - pigmented Demodex protrud- ing from the hair follicles (red arrows) (magnification x150; field of view 1.7 mm); (D) LM with numerous heavily-pigmented Demodex tails (red arrows) protruding from the hair follicles (magnification x30; field of view 7.5mm); (E) Clustered, entirely pigmented, and elongated bodies of Demodex (red arrow) within the hair follicle (magnification x150; field of view 1.7mm); (F) Solar lentigo – Demodex detected under super-high magnification dermoscopy as round brown structures (red arrow) inside the hair follicle (magnification x150; field of view 1.7 mm). Research Letter | Dermatol Pract Concept. 2024;14(1):e2024044 3 should be distinguished from the pigmented variant of de- modicosis, PD. The pigmentation within Demodex folliculorum has been predominantly observed by us in LM. However, we have also encountered a case of solar lentigo with heavily pigmented Demodex inside the hair follicle. Therefore, both the diagnostic significance and the origin of the pigment need further research. References 1. Forton FMN. The pathogenic role of Demodex mites in rosacea: A potential therapeutic target already in erythematotelangiec- tatic rosacea? Dermatol Ther (Heidelb). 2020;10(6):1229-1253. DOI: 10.1007/s13555-020-00458-9. PMID: 33095403. PMCID: PMC7649190. 2. Chen W, Plewig G. Human demodicosis: revisit and a proposed classification. Br J Dermatol. 2014;170(6):1219-1225. DOI: 10.1111/bjd.12850. PMID: 24471456. 3. Bertold C, Martel P, Passeron T, Bahadoran P. 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