Dermatology: Practical and Conceptual Research Letter | Dermatol Pract Concept. 2022;12(1):e2022002 1 Crusted Umbilicated Papules in a Child Hitaishi Mehta1, Sheetanshu Kumar1, Divya Aggarwal2, Debajyoti Chatterjee2, Keshavamurthy Vinay1 1 Department of Dermatology, Venereology and Leprology, Postgraduate Institute of Medical Education and Research, Chandigarh, India 2 Department of Histopathology, Postgraduate Institute of Medical Education and Research, Chandigarh, India Key words: reactive perforating collagenosis, RPC, perforating disorders Citation: Mehta H, Kumar S, Aggarwal D, Chatterjee D, Vinay K. Crusted umbilicated papules in a child. Dermatol Pract Concept. 2022;12(1):e2022002. DOI: https://doi.org/10.5826/dpc.1201a02 Accepted: April 14, 2021; Published: January 2022 Copyright: ©2022 Mehta et al. This is an open-access article distributed under the terms of the Creative Commons Attribution- NonCommercial License (BY-NC-4.0), https://creativecommons.org/licenses/by-nc/4.0/, which permits unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original authors and source are credited. Funding: None. Competing interests: None. Authorship: All authors have contributed significantly to this publication. Corresponding author: Keshavamurthy Vinay, MD, DNB, MNAMS, Department of Dermatology, Venereology and Leprology, Postgraduate Institute of Medical Education and Research, Chandigarh, India. E-mail: vinay.keshavmurthy@gmail.com. Introduction Reactive perforating collagenosis (RPC) is a rare benign per- forating disorder characterized by transepidermal elimina- tion of collagen fibers. Both familial and acquired forms of RPC exist, the latter in association with end-stage chronic kidney disease and diabetes mellitus. The very rare child- hood form has slight male predilection and is commonly familial [1]. Case Presentation Dermatology consultation was sought for a school-age child with multiple mildly itchy, red, raised lesions on his face and dorsum of hands, which were first noticed by the parents at 2 years of age. The parents also reported spontaneous healing of a few of the lesions with residual hypopigmented scars. Preceding history of insect bites or trauma was denied. He was born out of a non-consanguineous marriage, and no one in family had a history of similar lesions. Examina- tion revealed multiple skin-colored to erythematous discrete papules on both cheeks (Figure 1A) and dorsum of hands (Figure 1B) with central adherent keratotic plugs along with few well-circumscribed areas of atrophic scars. Dermoscopy of an individual lesion is presented in Figure 2A. Routine laboratory parameters including renal function tests, fast- ing blood sugar, and urinalysis were within normal limits. Histopathological examination of a facial papular lesion revealed compact ortho- and parakeratotic epidermis with a cup-shaped lesion lined by acanthotic epidermis on both sides along with mild perivascular and periadnexal lymph- omononuclear cell infiltrate mixed with collagen bundles in the dermis (Figure 2B). Altered collagen could be seen ex- truding trans epidermally through the cup-shaped depres- sion. A diagnosis of RPC was reached. The child was treated with topical tretinoin 0.025% ointment with satisfactory improvement after 1 month. Conclusions Familial RPC commonly presents as erythematous papules with central adherent scale-crust over the extensor aspect of 2 Research Letter | Dermatol Pract Concept. 2022;12(1):e2022002 extremities. Superficial trauma precedes most lesions. Indi- vidual lesions heal within 6-10 weeks, but recurrences are common. Although the familial and acquired forms appear similar in morphology and on histopathology, the acquired form tends to be more persistent and shows transepidermal elimination of both collagen and elastin. The central homogeneous yellowish area observed on der- moscopy corresponds to the central scale or crust, and the white rim of varying thickness corresponds to the epidermal invagination, along with an erythematous halo which arises due to small blood vessels around the lesion [2]. Histopathol- ogy reveals a plug of keratotic debris with vertically oriented collagen fibers extending into the plug, along with parakerato- sis, epithelial hyperplasia, and dyskeratotic keratinocytes [1]. The diagnosis is mostly clinical and requires histopa- thology for confirmation. Investigations other than punch Figure 1. (A) Multiple skin-colored to erythematous discrete papules on left cheek with central adherent keratotic plugs along with few well circumscribed areas of atrophic scars on cheek. (B) Crusted umbilicated papules over dorsum of both hands. Figure 2. (A) Dermoscopy reveals a yellowish central homogenous area along with a white rim surrounded by erythematous halo at the periphery (DermLite II, Hybrid M, ×10, polarized). (B) Histopathological examination (H&E, ×40) of the punch biopsy taken from one of the papular lesions on the face showing orthokeratotic epidermis with a cup shaped lesion lined by acanthotic epidermis on both sides along with mild perivascular and periadnexal lymphomononuclear cell infiltrate mixed with collagen bundles in the dermis. The cup-shaped lesion was densely packed with degenerated basophilic collagen bundles. Research Letter | Dermatol Pract Concept. 2022;12(1):e2022002 3 biopsy are neither necessary nor contributory. Differential diagnosis includes papular urticaria, prurigo nodularis, per- forating folliculitis, and elastosis perforans serpiginosa. Along with avoidance of trauma, topical therapies re- ported to be successful include retinoids, corticosteroids, and salicylic acid. Other therapies are systemic antihistamines, retinoids, methotrexate, photochemotherapy, NB-UVB, and cryotherapy. Most of the patients have a relapsing-remitting course throughout their lifetimes. Childhood RPC is a rare entity with an obscure etio- pathogenesis and usually self-limiting course. Awareness among clinicians regarding this entity is imperative in order to avoid misdiagnosis, anxiety among parents, and over-ag- gressive management. Informed consent: Informed consent for publication of clini- cal details and clinical images was obtained from the patient. References 1. Millard PR, Young E, Harrison DE, Wojnarowska F. Reactive perforating collagenosis: light, ultrastructural and immuno- histological studies. Histopathology. 1986;10(10):1047-1056. DOI:10.1111/j.1365-2559.1986.tb02541.x. PMID: 2430879. 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: 26114057. PMCID: PMC4462904.