Scabies Evaluated by Dermoscopy and Fluorescence Microscopy: A Case Report

Li-Wen Zhang, Wen-Ju Wang, Xue-Ying Liu, Lei Xu, Lu Zheng, Cong-Hui Li, Yong-Hong Lu

Department of Dermatovenereology, Chengdu Second People’s Hospital, Chengdu, Sichuan 610017, China.

Abstract Introduction: Scabies is an infectious skin disorder caused by the mite Sarcoptes scabiei.The diagnosis of scabies is often confirmed by microscopic detection of scabies mites, eggs, or feces.We herein describe the diagnosis of scabies in a boy with the assistance of dermoscopy and fluorescence microscopy.Case presentation: A 16-year-old Chinese boy presented with a 2-month history of extensive papules and excoriations with intense pruritus on the trunk and limbs.Dermoscopy showed a sinuous burrow in the finger webs with a brown jet-shaped triangular structure at the end.A fluorescence microscopy revealed a hatching egg and a mite.The boy was diagnosed with scabies and treated with 5% sulfur ointment.Discussion: The use of dermoscopy in patients with scabies reveals a sinuous burrow with a brown jet-shaped triangular structure composed of the pigmented head and anterior legs of the mite[1].A fluorescence microscopy revealed mites and eggs with blue fluorescence after staining, allowing us to easily identify scabies.Conlcusion: The combination of dermoscopy-guided tape testing with fluorescence staining technology may enhance the diagnostic accuracy and efficiency of scabies.

Keywords: scabies, dermoscopy, fluorescence, case report

Introduction

Scabies is an infectious skin disorder caused by the miteSarcoptes scabiei.Classic scabies typically manifests as intensely pruritic lesions with a characteristic distribution.The sides and webs of the fingers,wrists,axillae,areolae,and genitalia are common sites of involvement.The diagnosis of scabies is often confirmed by microscopic detection of scabies mites, eggs, or feces.We herein describe the diagnosis of scabies in a boy with the assistance of dermoscopy and fluorescence microscopy.The improvement in method of testing may enhance the diagnostic accuracy and efficiency of scabies.

Case report

A 16-year-old Chinese boy presented with a 2-month history of extensive papules and excoriations with intense pruritus on the trunk and limbs,especially the finger webs,wrists, axillae, areolae, umbilicus, lower abdomen, and genitals (Fig.1).Two months ago, one of his roommates had been diagnosed with scabies.Dermoscopy showed a sinuous burrow in the finger webs with a brown jet-shaped triangular structure at the end (Fig.2A).Interestingly,dermoscopic examination revealed a mite moving rapidly and irregularly in the patient’s finger webs.We then placed the mite on a glass slide using transparent adhesive tape and observed it by dermoscopy(Fig.2B).Next,we added a drop of fluorescent whitening agent onto the glass slide and observed a hatching egg with bright blue fluorescence(Fig.2C) and a mite with dark fluorescence (Fig.2D)through a fluorescence microscope.The boy was diagnosed with scabies and started treatment with 5% sulfur ointment.His lesions and pruritus were resolved after 2 weeks of treatment.The patient gave his agreement to publish his case.

Figure 1. Clinical features of the patient with scabies.Extensive papules and excoriations with intensepruritus on the lower abdomen,and genitals.

Figure 2. Dermoscopy and fluorescence microscopy images of the lesions from patient with scabies.Dermoscopy showed a sinuous burrow with a brown jet-shaped triangular structure at the end(A)and a mite on the glass slide(B).Fluorescence microscopy(×100)showed a hatching egg with bright blue fluorescence (C) and a mite with dark fluorescence (D).

Discussion

Dermoscopy is a noninvasive and convenient examination method that has been widely used in the diagnosis of many skin diseases.The use of dermoscopy in patients with scabies reveals a sinuous burrow with a brown jetshaped triangular structure composed of the pigmented head and anterior legs of the mite.1The diagnosis of scabies can only be confirmed by observation of mites.In the past,the adhesive tape test and skin scraping procedure were the most commonly used auxiliary diagnostic methods for scabies.These methods have a high specificity in diagnosing scabies, but their low sensitivity cannot exclude the possibility of scabies.A prospective, nonrandomized, evaluator-blinded, non-inferiority study of 238 patients comparing the diagnosis of scabies using dermoscopyvs.traditional skin scraping demonstrated that dermoscopy is a useful tool for diagnosing scabies;it exhibited a high sensitivity, even in inexperienced hands,and greatly enhanced the physician’s clinical skills for making treatment decisions.2Another study of 100 patients comparing the diagnostic properties of adhesive tape,skin scraping,and dermoscopy in diagnosing scabies suggested that dermoscopy-guided tape testing may be a helpful tool for the diagnosis of scabies.3

Ourc linical work has shown that tape testing of scabies has a higher positivity rate and is less time-consuming when performed under the guidance of dermoscopy, especially when combined with fluorescence staining technology.First,we use dermoscopy to identify characteristic lesions (a sinuous burrow with a brown jet-shaped triangular structure) in specific locations.We then take samples from these locations with transparent adhesive tape.Under a fluorescence microscope, mites and eggs exhibit blue fluorescence after staining with a fluorescent whitening agent,allowing us to easily identify the mites and eggs and clearly observe their forms.The fluorescent whitening agent can combine with chitin,which universally exists in nature,including in fungal cell walls, the carapace of insects, and crustacean shells.The combination of dermoscopy-guided tape testing with fluorescence staining technology may improve the diagnostic accuracy and efficiency of scabies,which needs a big sample size of studies to verify.

In conclusion, as a noninvasive and convenient examination tool, dermoscopy is useful in the diagnosis of scabies.The combination of dermoscopy-guided tape testing with fluorescence staining technology may enhance the diagnostic accuracy and efficiency of scabies.