Dermatology: Practical and Conceptual Letter | Dermatol Pract Concept 2021;11(1):e2020085 1 Dermatology Practical & Conceptual Introduction Acquired perforating dermatosis (APD) is a cutaneous dis- order characterized by transepidermal elimination of dermal connective tissue. Acquired reactive perforating collagenosis (ARPC), the most common form of APD, is usually asso- ciated with underlying diabetes mellitus and chronic renal failure. Here we aimed to demonstrate dermoscopic patterns of ARPC in a series of 7 patients. Case Presentation A total of 60 lesions from 7 patients with a histopathologi- cal diagnosis of ARPC were evaluated. The mean age of the patients was 56 years and the majority was male (n=6). The most common clinical manifestations were itchy, crusted papules (Figure 1A) followed by excoriated papules (Figure 1B) and white-to-brown macules (Figure 1C). The mean disease duration was 10 months. The most common local- ization of the lesions was on the lower extremities (n=7). Four patients had generalized lesions involving the lower extremities and trunk. All recruited patients had diabetes mellitus. Diabetes mellitus was accompanied by renal failure in one of the patients. A total of 5 different dermoscopic patterns were identified (Figure 2) and illustrated (Figure 3). Pattern 1 (n=14, 23%) showed a white rim surround- ing a central yellow-to-brown structureless area. The most common pattern was pattern 2 (n=21, 35%), which was composed of a central yellow–to-brown structureless area and blood spots surrounded by a collarette of scale, a periph- eral pinkish structureless area, and dotted vessels. Pattern 3 (central white structureless area surrounded by curved lines and brown reticular lines; n=10, 17%) and pattern 5 (cen- tral multicolor structureless areas including red, brown and white areas, surrounded by brown reticular lines; n=7, 12%) were characteristic of the late and healed lesions. Pattern 4 (n=8, 13%) was characterized by central blood spots and concentric white-to-brown rims possibly associated with scratching of the lesions. Four patients showed more than 1 pattern. Histopathological examination of all samples revealed an invaginating epidermal process composed of hyperkeratosis overlying a cup-shaped depression and tran- sepidermal elimination of eosinophilic altered collagen fibers (Figures 4 and 5). Dermoscopic Patterns of Acquired Reactive Perforating Collagenosis Ömer Faruk Elmas1, Asuman Kilitci2, Belkiz Uyar1 1 Department of Dermatology, Faculty of Medicine, Kirşehir Ahi Evran University, Kirşehir, Turkey 2 Department of Pathology, Faculty of Medicine, Kirşehir Ahi Evran University, Kirşehir, Turkey Key words: dermoscopy, perforating dermatosis, perforating collagenosis, transepidermal elimination Citation: Elmas ÖF, Kilitci A, Uyar B. Dermoscopic patterns of acquired reactive perforating collagenosis. Dermatol Pract Concept. 2021;11(1):e2020085. DOI: https://doi.org/10.5826/dpc.1101a85 Accepted: May 6, 2020; Published: December 7, 2020 Copyright: ©2020 Elmas et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License BY-NC-4.0, which permits unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: None. Competing interests: The authors have no conflicts of interest to disclose. Authorship: All authors have contributed significantly to this publication. Corresponding author: Ömer Faruk Elmas, MD, Department of Dermatology, Faculty of Medicine, Kirşehir Ahi Evran University, Kirşehir, 40000, Turkey. Email: omerfarukmd@gmail.com 2 Letter | Dermatol Pract Concept 2021;11(1):e2020085 reported in previous studies [1,2]. Patterns 4 and 5 have apparently not been identified in previous studies. In this study, only well-established lesions (patterns 1 and 2) were biopsied to achieve a definitive diagnosis, and all specimens showed typical histopathological features of the entity. The histopathological counterpart of the central yellow-to-brown structureless area is central keratin debris. The peripheral Conclusions There are very few reports on the dermoscopic features of ARPC [1,2]. In this case study, we identified a total of 5 different dermoscopic patterns. Pattern 1 and pattern 2 pos- sibly indicate well-established lesions, and the dermoscopic findings represented by these patterns were similar to those Figure 1. Acquired reactive perforating collagenosis with different stages of le- sions. (A) Crusted and (B) excoriated papules and (C) white-to-brown mac- ules. A B C Figure 2. Different dermoscopic pat- terns of acquired reactive perforating collagenosis: (A) pattern 1; (B) pattern 2; (C) pattern 3; (D) pattern 4; and (E) pattern 5. A B C D E Letter | Dermatol Pract Concept 2021;11(1):e2020085 3 white rim and collarette of scale prob- ably reflect invaginating epidermal hyperplasia. The possible histopatho- logical counterpart of the central white structureless area is fibrotic collagen formation in the dermis. The peripheral pinkish structureless area and dotted vessels may represent dermal inflam- matory reaction with superficial dilated vessels. Peripheral brown reticular lines may correspond to hyperpigmented basal keratinocytes. To conclude, dermoscopy may be a useful diagnostic tool in suspected cases of ARPC. The peculiar dermoscopic patterns we identified may lead the way to more comprehensive studies. Figure 3. Illustration of the dermoscopic patterns identified for acquired reactive perforating collagenosis. Figure 4. Acquired reactive per- forating collagenosis. (A) A cup- shaped epidermal invagination with keratin and inflammatory debris (H&E, ×50) and (B, C) transepidermal elimination of ver- tically oriented altered collagen (H&E, ×200; ×400). A B C Pattern 1 Central yellow-to-brown structureless and blood spots surrounded by a whithe rim, peripheral pinkish structureless, dotted vessels Pattern 2 Central yellow-to-brown structureless and blood spots surrounded by a collarette of scale, peripheral pinkish structureless Pattern 3 Central white structureless surrounded by curved lines and brown reticular lines Pattern 4 Central yellow-to-brown hemorrhagic crust, surrounded by concentric brown and white rims Pattern 5 Central multicolor structureless areas including red, brown and white surrounded by brown reticular lines 4 Letter | Dermatol Pract Concept 2021;11(1):e2020085 Dermatol Pract Concept. 2018;8(4):303-305. DOI: 10.5826/ dpc.0804a11. PMID: 30479861. 2. Kittisak P, Tanaka M. Dermoscopic findings in a case of reactive perforating collagenosis. Dermatol Pract Concept. 2015;5(2):75-77. DOI: 10.5826/dpc.0502a13. PMID: PMID: 26114057. Acknowledgement We would like to thank Beyza Nur Elmas for illustrating the dermoscopic patterns. References 1. Ormerod E, Atwan A, Intzedy L, Stone N. Dermoscopy features of acquired reactive perforating collagenosis: a case series. Figure 5. Acquired reactive perforat- ing collagenosis. Hyperkeratosis over- lying the cup-shaped depression in the epidermis may correspond to central yellow-to-brown structureless area ob- served on dermoscopic examination. Epidermal hyperplasia adjacent to the cup-shaped depression with overlying hyperkeratosis may reflect (A) dermo- scopic peripheral white rim and collar- ette scale (H&E, ×50). (B) Transepi- dermal elimination of altered collagen (H&E, ×400) and (C) superficial der- mal fibrotic collagen bundles (H&E, ×200) may correspond to dermoscopic white structureless areas. (C) Superfi- cial dermal vessels and perivascular in- flammatory infiltration may represent dermoscopic peripheral pinkish struc- tureless areas and dotted vessels. A B C