Dermoscopy Aids in the Diagnosis of Discoid Lupus Erythematosus

Herein, we present a protocol to demonstrate the utility of dermoscopy in rheumatic diseases. In addition, we described the dermoscopic manifestations of discoid lupus erythematosus skin lesions.

Dermoscopy is an important non-invasive form of examination that plays a critical role in the diagnosis of rheumatic diseases accompanied by skin lesions. This technique is performed in real-time and can thus assist in determining the skin biopsy site. Skin lesions are common and important manifestations of most rheumatic diseases, including lupus erythematosus. In some rheumatic diseases, such as rheumatoid arthritis, the incidence of skin rashes may not be as high; however, those lesions that do develop can be diverse and deceptive, thereby complicating diagnosis. Dermoscopy and the observation of microscopic characteristics can assist in diagnosing primary diseases in their early stages. Herein, we present a protocol that provides a detailed overview of the standardized operation process of dermoscopy. Further, using discoid lupus erythematosus as an example, we demonstrate the important role of dermoscopy in the diagnosis of many different rheumatic diseases. Finally, we discuss the diverse dermoscopic manifestations of different rheumatic diseases and their associated skin lesions.

Dermoscopy is an emerging non-invasive diagnostic technique that has been widely applied in various dermatological diseases, playing an important role in the early stages of diagnosis. It is becoming increasingly used in the diagnosis of inflammatory and rheumatic diseases. This technique has the advantages of being non-invasive and performed in real-time, thus assisting in determining the site of skin biopsy. The basic principle of dermoscopy involves the use of a liquid interface or polarized light technology to reduce the backscattered light caused by the skin's stratum corneum; this allows magnification of lesions by a factor of tens to hundreds, facilitating further observation of the structure under the stratum corneum and even the superficial dermis. This visualization not only aids in the diagnosis and differential diagnosis of the disease but also helps in guiding the treatment and judging treatment efficacy¹. This technique circumvents the pain, trauma, and scarring caused by invasive examinations and reduces pain in patients. Currently, two types of dermoscopy are applied: polarization (Dermoscopy Polari-light, DP) and infiltration (Dermoscopy Soakage, DS)². Classical dermoscopy is performed by infiltrating the skin with fluid to increase light transmission and reduce the amount of reflected light. Polarized light dermoscopy, which has been developed in recent years, further allows the observation of subcutaneous structures without the use of an infiltrating solution by filtering out diffusely reflected light from the skin surface using a polarizing filter.

Discoid lupus erythematosus (DLE) is the most common form of cutaneous lupus which generally affects sun-exposed areas such as the face, scalp, and upper trunk. The skin lesions in patients with DLE show significant variation. Differentiating DLE lesions on the scalp and other areas from inflammatory, neoplastic, or infectious diseases may be challenging in some cases. Currently, DLE can be diagnosed using methods such as clinicians' observation of skin lesions, skin biopsy, and non-invasive examinations like dermoscopy. Skin biopsy has long been an important method for DLE diagnosis, as pathological analysis of tissue samples provides reliable evidence. However, it has limitations. It is an invasive procedure, causing pain to patients and carrying risks such as infection, bleeding, and scarring, which may lead some patients to refuse it. Moreover, the tissue samples are limited, with a risk of sampling error. If the sample is not from a typical lesion area, misdiagnosis or missed diagnosis may occur. The pathological examination is complex and time-consuming, usually taking days to weeks, potentially delaying treatment. It is also difficult to perform a biopsy of every suspected DLE skin lesion. Additionally, visual inspection cannot reveal deep-layer skin structures and lesion details, making it difficult to diagnose early hidden lesions or cases with unobvious appearance changes during disease progression.

Dermoscopy can aid with early differential diagnosis and selection of suitable sites for skin biopsy. It can also provide more detailed information that is difficult to observe with the naked eye and has obvious advantages in improving diagnostic accuracy, sensitivity, and specificity³, assisting in disease staging and assessment, and differential diagnosis. Therefore, it is a very effective adjuvant diagnostic tool. This examination can be performed on infants, pregnant women, and the elderly without any absolute contraindications. From a pathological perspective, DLE lesions are mainly characterized by epidermal hyperkeratosis, formation of follicular plugs, liquefaction degeneration of basal cells, and lymphocytic infiltration around the blood vessels and appendages in the superficial dermis⁴. The features observed under dermoscopy are the direct reflection of these pathological changes on the skin surface. For example, follicular plugs present as black or brown punctate or conical structures under dermoscopy, which is consistent with the pathological changes of hyperkeratosis of follicular epithelial cells and accumulation of keratinous substances at the follicular orifice. Vascular dilation and abnormal morphology are related to the vascular changes caused by inflammation around the blood vessels in the superficial dermis³.

The protocol was approved by the Ethics Committee of Shanghai Dermatology Hospital. The study obtained consent from the patient/participant to use the images/data in the publication.

1. Preparation

1. Patient screening
   1. Begin by reviewing the patient's medical history and conducting a physical examination.
   2. Identify patients with suspected DLE, particularly those with erythema on the face and other exposed areas, often accompanied by adherent scales. While these areas are typically affected, consider other locations as well.
2. Contraindications
   1. When performing this procedure, despite the absence of absolute contraindications, categorically exclude patients incapable of cooperating with the examination or refusing to undergo the procedure.
3. Preparing the examination environment
   1. Ensure the examination room is well-lit. Open the blinds or curtains to allow natural light to fill the room.
   2. If natural light is insufficient, use additional artificial lighting that provides clear, even illumination.
   3. Set the room temperature (RT) to a comfortable level, typically around 20-25°C. Ensure the room is clean, organized, and free from distractions or obstructions.

2. Dermoscopy examination procedure

1. Patient positioning
   1. Guide the patient into the examination room and have the patient sit on the examination chair or lie on the examination bed, if necessary. Position the examination chair against a black curtain or similar background to expose the skin lesions fully.
   2. Cleanse the skin with a mild, non-irritating cleanser(75% alcohol swabs) to remove oil, dirt, or cosmetics. For areas such as the scalp that require shaving, carefully shave the area using a clean, sharp razor, avoiding abrasions or cuts. Ensure that the skin is completely dry before proceeding to the next step.
2. Examination process
   1. Double-click the software icon in the computer system to start the dermoscopy. Check the dermoscopy device's magnification levels (usually 20× to 40×) and the quality of polarized light and ensure the overall functionality of the device.
   2. Use the high-definition camera mode of the dermascope to capture a general photograph of the skin lesions.
   3. Disinfect the lens of the dermatoscope with a cotton ball soaked in 75% alcohol and gently dry it.
   4. Gently place the dermoscopy on the skin's surface to examine. Slowly adjust the focus knob until the skin lesion is clearly visible.
   5. Switch the polarized light mode to enhance the visibility of the skin structures.
   6. Observe the shape of the lesion, noting any irregularities or asymmetries.
      1. Examine the color for any variations in pigmentation. Inspect the vascular structure, paying attention to the pattern and density of blood vessels; thick arborizing vessels are always detected in DLE skin lesions.
      2. Adjust the magnification by pressing the + and - buttons on the lens to view the lesion from different angles, ensuring that all relevant details are captured.
   7. Hold the dermoscopy steadily with the hand and gently change the angle between the dermoscopy and the skin surface. Make sure to move slowly and slightly to avoid large changes that could affect the observation.
   8. Continuously observe the image in the dermoscopy and stop adjusting when the image is clearest.

3. Recording and analysis

1. Feature recording
   1. Document the dermoscopic features of the skin lesions and make a detailed descriptive record of the lesions. Skin lesions such as black or brown punctate structures at the hair follicle orifices, red arborizing vessels, and punctate or circular vessels around the hair follicles are often observed in cases of DLE.
2. Final diagnosis
   1. After completing the dermoscopic examination and gathering all necessary information, review the patient's clinical manifestations, medical history, and other relevant examination results. Based on this comprehensive assessment, make a final diagnosis.
3. Recommendations and follow-up
   1. If the diagnosis is clear, provide the patient with appropriate recommendations, which may include lifestyle modifications, topical treatments, or referrals to other specialists.
   2. If further examination or treatment is required, explain the need for additional steps in detail. Develop a follow-up plan outlining the next steps, the expected timeline for follow-up, and any specific instructions or precautions for the patient.

Dermoscopy of facial (non-scalp areas) DLE reveals several different features according to the stage of the disease and location of skin lesions (non-scalp vs. scalp). According to one prior literature review⁵, the most common findings in scalp DLE are follicular keratotic plugs, followed by absent follicular ostia and fibrotic white, yellow, black, and red dots. In contrast, the most common dermoscopic features of the follicular openings in non-scalp DLE lesions were keratotic plugs, red dots, and dilated follicles. Follicular keratotic plugs, red dots, large yellow or yellow-brown dots, and white scaling are the most common characteristic features of early and active scalp DLE. White structureless areas (white patches), milky red areas, loss of follicular openings, and "red spiders on yellow dots" are generally observed in end-stage inactive scalp DLE. Thick arborizing vessels were detected at the periphery of both active and late DLE lesions⁶. Linear vessels are more frequently documented in non-scalp DLE cases, whereas arborizing, dotted, hairpin and coiled vessels are more frequently documented in scalp DLE cases. The characteristics of dermoscopy in specific areas are noteworthy. The most common feature of labial DLE is telangiectasia, followed by brown pigment spot scales, white structureless areas, bleeding spots, and erosions⁷. One study previously reported the presence of a pterygium and distal onycholysis associated with white avascular areas, tortuous vessels in the eponychium and fine scales, and pointed vessels in the hyponychium⁸. DLE is further characterized by a wide variety of dermoscopic findings. The dermoscopic manifestations of DLE need to be distinguished from those of multiple diseases, such as rosacea, seborrheic dermatitis, and lichen planus⁹. The typical manifestations of seborrheic dermatitis observed on dermoscopy are dotted vessels and yellow scales. Under dermoscopy, rosacea often presents as "polygonal vessels". Thus, clinicians should carefully consider the dermoscopic manifestations of DLE. Dermoscopy diagnosis needs to be combined with the patient's medical history, serum blood tests, and, when necessary, ultrasound, confocal microscopy, and biopsy for a comprehensive diagnosis.

Here, we present a non-scalp skin lesion (Figure 1), and its dermoscopic manifestations in a male patient with DLE (Figure 2 and Figure 3), including a small number of scales and red horn plugs at the hair follicle opening, surrounded by a red halo.

Figure 1: Facial skin lesions of a male patient with DLE. Erythema on the tip of the nose, with mild infiltration. Please click here to view a larger version of this figure.

Figure 2: Dermoscopic manifestations in a male patient with DLE. A small number of scales and red horn plugs at the hair follicle opening, surrounded by a red halo. (Magnification: 20×,polarized light mode) Please click here to view a larger version of this figure.

Figure 3: Dermoscopic manifestations in a male patient with DLE. A small number of scales and red horn plugs at the hair follicle opening, surrounded by a red halo. (Magnification: 30×, polarized light mode) Please click here to view a larger version of this figure.

Dermoscopy is a non-invasive, convenient, and real-time alternative to skin biopsy. In 1920, Saphier used dermoscopy to examine nevus and melanoma lesions and made a descriptive diagnosis based on skin color and morphology¹⁰. In 2001, the International Conference on Dermatology established unified diagnostic criteria for dermoscopy. Recently, research on digital dermoscopy has also rapidly increased. The DP method is a microscopic digital imaging technology first developed in the 21st century², mainly composed of light-emitting diodes with specific wavelengths. This technique effectively filters the interference of reflected light on the skin surface, thereby improving the visibility of skin lesions. The lens does not directly contact the skin and does not require any coupling agent, thus reducing the pressure on the skin and allowing for clear observation of deeper structures¹¹. Compared with the DS mode, the DP mode is more commonly applied in clinical examinations for scaly rashes and sensitive areas such as the eyes, mouth, and nose. This can reduce the rate of infection caused by direct contact. However, the image clarity obtained using the DS method was slightly better than that obtained using the DP method.

Dermoscopy was initially used for the early diagnosis of pigmentary and tumorous skin diseases. It plays an important role in pigmentary diseases. Dermoscopy patterns specific to sites include acral melanocytic lesions, specifically those with the parallel furrow pattern or parallel ridge pattern. The presence of these parallel patterns can be attributed to the distinct distribution of benign and malignant melanocytes¹².Currently, dermoscopy is widely used to treat inflammatory, vascular, and rheumatic diseases¹³. The disinfection method of the dermoscopy is convenient. We use 75% alcohol swabs to wipe the surface of the dermoscopy for disinfection. During dermoscopy examinations, artifacts and potential pitfalls may be encountered. Artifacts include reflection artifacts, motion artifacts, and focusing artifacts. Reflection artifacts occur because the presence of substances such as oils, moisture, or gels on the skin surface during dermoscopy may cause reflections, forming bright spots or stripes on the images. By adjusting the angle of the light source and properly cleaning the patient's skin, reflection artifacts can be effectively avoided. Motion artifacts are caused by slight movements of the patient during the examination, which lead to blurred images. Informing the patient to keep still before shooting and trying to shorten the shooting time during the examination can help obtain clear images quickly. Focusing artifacts are due to inaccurate focusing of the dermoscopy, resulting in blurring of some areas of the image. Therefore, adjusting the focal length correctly and readjusting it when switching magnifications can ensure the clarity of the images. Potential pitfalls include diagnostic traps, equipment problems, and operator differences. Since the dermoscopic manifestations of some skin diseases may be similar, they are prone to misdiagnosis. Combining a synthesis of multiple features, clinical symptoms, medical history, and other examination methods can improve diagnostic accuracy. The quality and performance of the equipment can also affect the examination results. It is necessary to regularly maintain and calibrate the equipment and repair or replace components in a timely manner when problems such as flickering light sources or blurred images are found. There may be differences in the interpretation of dermoscopic images among different operators. It is advisable to discuss reducing such differences through standardized training and operation procedures.

If the image is blurry, one can gently wipe the lens with a clean and soft lens cloth. If the focusing is inaccurate, the dermoscopy should first be adjusted to the low-magnification lens. After finding the target area, slowly adjust the focus knob until the image is clear. Then, switch to the high magnification lens as needed and adjust the focus again in the same way. If the light source is flickering, check whether the light source has poor contact or is aging. If there are data transmission problems, check whether the data cable is firmly connected. Try reconnecting the data cable. If the data cable is properly connected, one can restart the software or the computer. If the operation of the dermoscopy is laggy, it may be due to insufficient memory. Clean up the system's junk files to free up the memory. If there are problems that cannot be solved, record them in a timely manner and contact the technical engineer for assistance.

In summary, the advantages of dermoscopy are as follows: 1) it can assist in ascertaining the optimal biopsy location and contribute to a notable reduction in unnecessary biopsy and complication rates; 2) it enables more accurate delineation of the boundaries of skin lesions in tumorous skin diseases, assisting in determining surgical margins¹⁴; 3) its field of view for observing skin lesions is large, which can compensate for the limitations of observing a single pathological section in skin biopsy; 4) it is an effective examination method for the early and accurate diagnosis of diseases, and may aid dermatologists in differentiating between two or more conditions that are hardly distinguishable with the naked eye; and 5) it is real-time, and can reduce unnecessary skin biopsies, alleviating patient fear; 6) it is a relatively quick examination, which minimizes time and associated costs¹⁵. However, there are some limitations of dermoscopy: 1) it has strong subjectivity; 2) further improvement of diagnostic criteria is necessary to achieve wider application.

Overall, we posit that this non-invasive yet highly effective methodology will be more widely applied in the early diagnosis of rheumatic diseases, offering hope to a wider spectrum of patients.

The authors declare no conflicts of interests.

We thank the patient for providing written informed consent for the publication of the protocol details and images.