Study: Confocal microscopy effective in analyzing infestation of mites in human skin disease

Dermatology researchers outlines benefits of a non-invasive and rapid method in detecting mites of the genus Demodex

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n the diagnosis of skin conditions caused by parasitic mites, a recent research study has outlined distinct advantages in the use of confocal microscope over the usual light microscope.

“The article presented our reviews on methodological advances in the diagnosis of demodecosis via our own research on demodecosis diagnosis efficiency with the aid of fluorescence lifetime measurement using confocal laser scanning microscopy,” reported Alexey Kubanov from the State Scientific Center of Dermatovenereology and Cosmetology, along with his research colleagues from the Ministry of Healthcare of the Russian Federation, Moscow, Russia, in a study published in the inaugural issue of the open access peer-reviewed Journal of Surgical Dermatology.

Demodecosis is a skin disease caused by parasitic Demodex mites, principally Demodex folliculorum longus which live in the glands of hair follicles and Demodex folliculorum brevis which reside in sebaceous (oil) glands connected to hair follicles. While mites are generally common constituents in the human skin microflora and typically do not cause any clinical symptoms, they could protract the acuteness of the inflammatory process in chronic dermatoses, according to the study authors.

“Demodecosis is often diagnosed in patients with severe clinical forms of acne and rosacea. This fact suggests that the mites complicate the course of the diseases, and thus promoting the development of inflammatory elements,” they said.

Hence, according to the researchers, there is a need for advancements in the identification methods of Demodex mites in order to achieve effective treatment of these skin afflictions.

Diagnostic methods

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	Section of mite-infested primate skin showing Demodex mites as the elongate irregular brown bodies within the inflamed hair follicles (Image source: Alan R Walker)

The diagnosis of demodecosis is currently only possible via laboratory diagnostics physically locating the genus Demodex mites. “The most common method of laboratory diagnostics is based on the preparation of acarogram by counting larvae, nymphs, eggs and mites in adult stage,” the study said.

Detection of mites is technically quite straightforward procedure: eyelashes and/or eyebrows are plucked without damaging the hair follicles, or the skin is scraped at places where the greatest congestion of Demodex reside (typically the forehead, wings of nose, and chin areas) during the extraction of ducts’ contents of sebaceous glands, and then the tested material is examined under the microscope at low magnification.

An advantage of both these methods is the removal of mites not only from the surface of the skin but also directly from the sebaceous glands, as well as evaluating large affected areas. “However, there is a problem: it is not always possible to detect mites deeper in the sebaceous glands,” said Kubanov and his fellow research team.

“Another disadvantage is the epithelium trauma, which is associated with the relative painfulness of the procedure and the discomfort in patients after epilation,” they explained, further adding, “It should be noted that information on scraping method is less abundant, and negative analysis result of laboratory research does not prove the absence of mite infestations.”

Another diagnostic method used by dermatologists is carrying out surface biopsy, or a “scotch tape test”, wherein an adhesive is placed on an oil-free cover glass and then pasted onto the affected skin, after which the glass slide is examined under the microscope at low magnification.

“The advantage of the method is its ease of use, but skin epithelium trauma, difficulty in obtaining material from the nose wings, and incomplete sterility of the obtained samples are clear disadvantages,” the study said.

Skin biopsy with subsequent histology of the received samples, on the other hand, is another method – albeit more difficult –– for diagnosing demodecosis. “For this purpose, a small skin area is obtained either by puncture (punch) or excisional (scalpel) method,” the study described. “Histological study provides many advantages; in particular, it is possible to fully see the sebaceous glands and surrounding areas. The main disadvantages of this method include skin trauma with the formation of scar and the inability to examine a large area of the skin,” the study added.

Confocal microscopy

Despite the fact that the “gold standard” for the pathomorphological evaluation of normal and affected skin in dermatology is still biopsy followed by histological study, according to the Russian researchers, “there is always a demand in the applied medicine field for informative, high-tech and non-invasive diagnostic methods, which include confocal laser scanning microscopy,” they stated.

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Confocal microscopy uses scanning microscope with two-stage focus, hence called “confocal” due to the use of same foci. In modern confocal microscope, it uses laser as its light source. The focused laser beam illuminates a certain point of the skin and the back focus of the lens would coincide with the microscope’s front focus, resulting in images of a very thin layer of the examined object.

“The work of confocal microscope is based mainly on the ability of various structures of the skin to refract the laser light to obtain images of the epidermis and dermis layers, and to evaluate the state of the vessels of the skin and dermal fibers,” the authors said.

The advantage is that confocal laser scanning microscope makes it possible to visualize mites that are both found in the deeper layers of the skin and inaccessible to scarification, according to their report “This method…makes it possible to scan various layers of the skin that allows the determination of the depth of mite detection (≈46.63 microns), number of mites and also their size,” the study noted.

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Additionally, in comparison to conventional light microscopy, confocal laser scanning microscopy method has the advantages of its high-contrast images with high resolution, three-dimensional reconstruction and digital data processing, according to the researchers. Furthermore, the lack of epithelium trauma and painful procedures are other additional advantages of this method.

“Thus, confocal laser scanning microscopy is considered as a non-invasive and rapid method for detecting mites of the genus Demodex based on scientific findings in literatures,” the researchers concluded.

Co-authors of the study include Gallyamova Yulia and Anzhela Grevtseva from Russian Medical Academy of Postgraduate Education, Ministry of Healthcare of the Russian Federation.

The research paper is available online at http://www.jsurgdermatol.com.

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