Untitled Observation | Dermatol Pract Concept 2015;5(2):13 75 DERMATOLOGY PRACTICAL & CONCEPTUAL www.derm101.com Introduction Reactive perforating collagenosis (RPC) is the most com- mon type of acquired perforating dermatoses (APD), [1] and is characterized by umbilicated papules and plaques with central crusted ulceration. Pruritus is the most common symptom of RPC, and the lesions are most commonly found on the extensor surfaces of the extremities. This entity is his- topathologically characterized by invagination of the epider- mis and transepidermal elimination of collagen bundles. The pathogenesis of RPC is still somewhat unclear, but it has been reported that trauma resulting from scratching may induce damage to the epidermis or dermal collagen [1,2]. Moreover, RPC is commonly found in association with chronic renal failure and diabetes mellitus. Dermoscopy is a noninvasive technique that has been used in the diagnosis of APD [3], especially for perforating folliculitis (PF). However, to our knowledge, the dermoscopic features of RPC have not been previously described in the literature. Here, we report the dermoscopic features and their histological correlations in RPC as a means to improve the diagnosis of this condition. Case presentation A 46-year-old Thai woman presented with a one-month history of multiple pruritic ulcerated papules and plaques with yellowish crust on the upper and lower extremities (Figure 1). Differential diagnoses included prurigo nodularis, perforating granuloma annulare, factitious disorder, and Dermoscopic findings in a case of reactive perforating collagenosis Payapvipapong Kittisak1, Masaru Tanaka2 1 Division of Dermatology, Department of Medicine, Phramongkutklao Hospital, Bangkok, Thailand 2 Department of Dermatology, Tokyo Women’s Medical University Medical Center East, Tokyo, Japan Key words: reactive perforating collagenosis, dermoscopy Citation: Kittisak P, Tanaka M. Dermoscopic findings in a case of reactive perforating collagenosis. Dermatol Pract Concept 2015;5(2):13. doi: 10.5826/dpc.0502a13 Received: December 15, 2014; Accepted: February 4, 2015; Published: April 30, 2015 Copyright: ©2015 Kittisak et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: None. Competing interests: The authors declare no conflict of interest. Authorship: All authors have contributed significantly to this publication. Corresponding author: Masaru Tanaka, MD, PhD, Department of Dermatology, Tokyo Women’s Medical University Medical Center East, 2-1-10 Nishi-Ogu, Arakawa-ku, Tokyo 116-8567, Japan. Tel: +81 3 3810 1111. Fax: +81 3 3894 1441. E-mail: tanaka.twmu@gmail.com Figure 1A. Multiple ulcerated papules and plaques with yellowish crust on the upper and lower extremities. [Copyright: ©2015 Kittisak et al.] 76 Observation | Dermatol Pract Concept 2015;5(2):13 non-ulcerating red papules and nodules as main features and factitious disorder would show more linearly or irregularly shaped lesions. However, dermoscopic features of these con- ditions were not previously reported. A biopsy from an ulcerated papule on the thigh showed perforation through the epidermis forming a tunnel filled with cellular debris, covered with scale-crust. Thick collagen fibers were observed perforating through this tunnel. The area of perforation was not connected to the hair follicles. other acquired reactive perforating dermatosis. Dermoscopy showed a yellowish-brown structureless area in the center, a whitish rim and pink-white structureless area, and hairpin vessels observed at the periphery (Figure 2). She had several underlying diseases, including diabetes mellitus and chronic renal failure. She was on hemodialysis three times a week. A perforating disorder seemed to be the most probable because of these clinical and dermoscopic findings. Prurigo nodularis and perforating granuloma annulare would show Figure 1B. A close up photo of the lesion. [Copyright: ©2015 Kit- tisak et al.] Figure 2. Dermoscopy showing a yellowish-brown structureless area in the center and a white rim with an erythematous halo at the periphery of the lesion. [Copyright: ©2015 Kittisak et al.] Figure 3. (A) Cup–shaped ulceration with basophilic crust (hematoxylin and eosin, ×4). (C) Perforation through the epidermis forming a tunnel filled with cellular debris, covered with scale-crust. Thick collagen fibers were perforating through this tunnel (hematoxylin and eosin, ×10). (B, D) Transepidermal elimination of the collagen bundles (Masson-trichrome stain, ×4 and ×10). [Copyright: ©2015 Kittisak et al.] Observation | Dermatol Pract Concept 2015;5(2):13 77 [4]. Although recent reports suggest that allopurinol might be a good therapeutic option for RPC in some patients, treat- ment of RPC is difficult and still no standard therapy is avail- able [4-6]. The present case was treated with antihistamine and emollients and relieved the symptom. In the present case report, the dermoscopy-pathology correlations were evaluated in RPC (Figure 4). The homo- geneous yellowish-brown structureless area observed at the center of the lesion was found to correspond to the scale- crust; the whitish rim to the epidermal invagination, the thickness of which varied in some areas; and the pink-white halo seemed to correspond to a combination of small blood vessels surrounding the lesion. Further, the hairpin vessels at the periphery corresponded to the irregular vessels in the papillary dermis at the periphery of the lesion. Ramirez-Fort et al. first described the dermoscopic feature of APD in 2013, and confirmed the diagnosis of PF by clinical and histopathological examinations [3]. The dermoscopic fea- tures described included bright white clods and a structureless gray area surrounded by brown reticular lines. Although RPC is included in APD, the clinical, dermoscopic, and histologi- cal features are substantially different from those of PF. We speculate that the differences between APD and PF reported by Ramirez-Fort and those between RPC and PF reported herein are mainly owing to the different sizes of the lesion and due to the differences in ethnicity between the reported cases. In conclusion, the dermoscopic features of RPC include central yellowish-brown structureless areas and a whitish rim with a pinkish white halo, as well as some hairpin ves- sels at the periphery. These features seem to contribute to the diagnosis of RPC. References 1. Kim SW, Kim MS, Lee JH, et al. A clinicopathologic study of thirty cases of acquired perforating dermatosis in Korea. Ann Dermatol 2014;26(2):162-71. 2. Wagner G, Sachse MM. Acquired reactive perforating dermatosis. J Dtsch Dermatol Ges 2013;11(8):723-9. 3. Ramirez-Fort MK, Khan F, Rosendahl CO, et al. Acquired perforat- ing dermatosis: a clinical and dermoscopic correlation. Dermatol Online J 2013;19(7):18958. 4. Tilz H, Becker JC, Legat F, et al. Allopurinol in the treatment of acquired reactive perforating collagenosis. An Bras Dermatol 2013;88(1):94-7. 5. rüger K, Tebbe B, Krengel S, et al. Acquired reactive perforating dermatosis. Successful treatment with allopurinol in 2 cases. Hau- tarzt 1999;50(2):115–20. 6. Karpouzis A, Giatromanolaki A, Sivridis E, Kouskoukis C. Ac- quired reactive perforating collagenosis: current status. J Dermatol 2010;37(7):585–92. The dermis showed proliferation of small blood vessels and mild perivascular inflammatory cell infiltrate comprising lym- phocytes and a few neutrophils (Figure 3). Masson-trichrome staining showed transepidermal elimination of the collagen bundles. Based on these clinical and histological features, a diagnosis of RPC was established. Conclusions The pathogenesis of RPC is still unknown but it has been hypothesized that inherited susceptibility, diabetic vasculopa- thy, and hypoxic conditions may be the predisposing factors Figure 4. The homogeneous yellowish-brown structureless area at the center of the lesion corresponding to the scale-crust; the whitish ring-shaped rim to the epidermal invagination (EI), the thickness of which varied; and the pink-white halo seemed to correspond to a combination of small blood vessels surrounding the lesion. [Copy- right: ©2015 Kittisak et al.]