Analysis of image characteristics of scabies by reflection confocal microscope.

Abstract

Scabies is an infectious skin disease caused by scabies mites parasitic on the skin. Scabies mites often parasitize on thin and soft parts of the skin, such as finger seams and their sides, wrist curve, elbow fossa, armpit, periumbilical, waist, lower abdomen, genitalia, groin, and the inner side of the upper thigh,1 and they tend to occur in families or crowded people.2 On the premise of having typical skin lesions and medical history, the diagnostic rate of scabies is still high. However, some patients have atypical skin lesions and eczema like changes due to repeated scratching and irritation caused by severe itching. In addition, some patients have a relatively long medical history and no social history, which makes it difficult to diagnose scabies. As a result, scabies can be misdiagnosed clinically and delay the patient's condition. Generally, scabies are easily misdiagnosed as skin pruritus eczema and prurigo, etc. In the past, we mainly used direct microscopic examination and histopathological biopsy to diagnose scabies. Direct microscopic examination or biopsy to find scabies mites, eggs, or fecal balls is the gold standard for the diagnosis of scabies. However, the positive rate of clinical smear microscopy is low, and the operation time is long, which can cause discomfort to patients and cannot be well coordinated. Histopathological biopsy is an invasive examination, which is difficult for many patients to accept. Therefore, there are many limitations in the diagnosis of scabies by traditional auxiliary means. Reflective confocal microscope (skin CT) is a new skin imaging diagnostic technology. It has the characteristics of noninvasive, in vivo, real-time acquisition of skin lesions.3 It can scan the same skin lesions at multiple levels and times to improve the diagnostic rate. It has been widely used in the diagnosis of various skin diseases. However, there are few reports on the image characteristics of scabies under the reflective confocal microscope. Recently, in clinical work, we performed skin computed tomography (CT) examination on patients diagnosed with scabies. By collecting skin CT images of these patients, we summarized the characteristics of reflective confocal microscope images of scabies, and now we share them with you. The reflective confocal microscope features of scabies mainly include the following points: 1. sponge edema in the acanthous layer, formation of focal blisters in the epidermis, and low refractive liquid dark areas (Figure 1A,B). 2. The tunnel structure can be seen in the upper part of the cuticle and acanthus layer. Scanning layer by layer along the tunnel shows that the structure of scabies (scabies mite) with medium and low refraction can be seen (Figure 2A,B). The morphology of scabies mites is similar to that observed by direct microscopy (Figure 2C), forming a nest-like structure. Two pairs of forefoot of some scabies mites can be clearly seen. 3. Middle low refraction round or oval scabies egg structure can be seen in the middle upper part of acanthous layer, with clear boundary (Figure 3A,B). 4. In the back of scabies mite, there are many regular round or oval high refraction dung ball structures at the superficial layer of the epidermis, some of which are lumpy (Figure 4A,B). In these microscopic features, it is highly specific to find scabies mites, scabies eggs, or dung ball structures for the diagnosis of scabies, and scabies can be diagnosed when one of the three is found under skin CT. Through our observation, dung ball is the most common feature of reflex confocal microscope in scabies, and its sensitivity and specificity are high. It is of great significance to diagnose scabies. Through the above sharing, we believe that we have a clear understanding of the typical skin CT features of scabies, and we hope that the reflective confocal microscope can be used as an important auxiliary examination method for scabies diagnosis in the future to help clinicians better diagnose and differentiate scabies.