Dermoscopy and reflection confocal microscope features of pigmented prurigo

Background Pigmented prurigo (PP) is a chronic and recurrent inflammatory skin disease. PP is not common clinically, but it is easily misdiagnosed because of its diversified clinical manifestations in different stages. Materials and methods We retrospectively analyzed the clinical, histopathological, dermoscopy, and reflectance confocal microscopy (RCM) features of 20 patients diagnosed as PP. Results The female predominance ratio was revealed with male to female of 1:4. Seven female patients were on a diet (without staple food) and one patient had a history of diabetes. Eight cases were suffered in spring, six cases in winter, three cases in summer, and three cases in autumn. Multiple sites were involved in 13 cases. Four patients had urticarial papules and plaques. Nineteen patients had erythematous papules with reticular distribution, of which 14 cases accompanied reticulate hyperpigmentation, four cases with papulovesicle, and two cases accompanied with pustules. One patient only showed reticulate hyperpigmentation. In the early lesions, dermatoscopy showed pink oval lesions, punctate or linear vessels, and pale yellow rings around the skin lesions. RCM is characterized by spongiosis, spongy vesicle, neutrophils scattered in the epidermis, which was consistent with epidermis spongiosis, neutrophils infiltrating into the upper epidermis and necrotic keratinocytes in histopathology. In the fully developed lesions, dermatoscopy showed pink lesions with brown pigment granules in the center and linear vessels in the edge. RCM showed that demarcation of epidermis and dermis is not clear, and inflammatory cells can be seen in the upper dermis and histopathologically lesions assumed a patchy lichenoid pattern, and the inflammatory cells infiltrating the dermis were dominated by lymphocytes. In the late lesions, dermatoscopy showed grainy grayish‐brown or yellowish‐brown pigmentation surrounding the hair follicle merging with each other. RCM showed that pigment granules were increased on the ring of basal cells, inflammatory cells were sparsely infiltrated in the dermal papilla and superficial layer, and epidermis slightly hyperplastic, with melanophages and a few lymphocytes infiltrating the superficial dermis in histopathology. Conclusion PP is easily misdiagnosed and not always occurs in those on a restrictive diet. A combination of dermatoscopy and RCM is helpful for its diagnosis of PP.