LETTERS TO THE EDITOR 70 ITaLIan JOuRnaL Of DERmaTOLOgy anD VEnEREOLOgy December 2021 (Cite this article as: Piccolo V, Corneli P, ferrara g, Russo T, Santoro C, Ronchi a, et al. Superimposed Blaschkoid lichen planus pigmentosus. Ital J Dermatol Venereol 2021;156(Suppl. 1 to no. 6):69-70. DOI: 10.23736/ S2784-8671.19.06379-X) © 2019 EDIZIOnI mInERVa mEDICa Online version at http://www.minervamedica.it Italian Journal of Dermatology and Venereology 2021 December;156(Suppl. 1 to no. 6):70–1 DOI: 10.23736/S2784-8671.19.06380-6 Plantar pilonidal sinus: diffcult to detect without the use of dermoscopy We recently came across three slightly pigmented yellowish pap- ules of the sole belonging to a 2-year-old child, 8-year-old child and 45-year-old man that are shown respectively in figure 1a-C. The lesions were painless except for the 8-year-old baby that referred the presence of a lot of pain. The three lesions were previously la- belled and unsuccessfully treated as warts. Dermoscopy made the diagnosis clear, showing clear-cut hairs (linear or coiled) (figure 1D) below a normal stratum corneum, easily extracted through a blade, thus supporting the diagnosis of plantar pilonidal sinus (PPS). Microscopic examination of extracted material confrmed that it was hair in the child, whereas in the adult patient it was found to be dark-colored textile fbers mimicking hair at dermos- copy (Supplementary Digital material 1: Supplementary figure 1). tal usually preceding the others. In literature, many cases of BLP associated to LRP are reported, but the patients usually showed the appearance of segmental manifestation followed by non-segmental (Supplementary Digital material 1: Supplementary Table I). In our patient, Blasckhoid lesions appeared on the trunk after 20 years of stable disease another part of the body, so we can assert that this is the frst reported case of “superimposed segmental manifestation” with an opposite behavior. The unexpected linear spread in differ- ent sites from the primary lesion of the knee, lead us to speculate about a second unidentifed etiologic mechanism causing an out- break limited to genetic susceptible areas. In conclusion, a better understanding of the genetic mechanism underlying infammatory dermatoses could improve our awareness regarding the etiology, improving the treatments for these polygenic disorders. Vincenzo PICCOLO 1 *, Paola CORnELI 2 , giuseppe fERRaRa 3 , Teresa RuSSO 1 , Claudia SanTORO 4 , andrea ROnCHI 5 , Iris ZaLauDEK 2 , Roberto aLfanO 6 , giuseppe aRgEnZIanO 1 1 unit of Dermatology, Luigi Vanvitelli university of Campania, naples, Italy; 2 unit of Dermatology, maggiore Hospital, university of Trieste, Trieste, Italy; 3 unit of Dermatology, Ospedale di udine, udine, Italy; 4 Center of Reference for Neurofbromatosis, Department of Women, Children and general and Specialist Surgery, Luigi Vanvitelli university of Campania, naples, Italy; 5 unit of Pathology, Department of mental and Physical Health and Preventive medicine, Luigi Vanvitelli university of Campania, naples, Italy; 6 Department of anesthesiology, Surgery and Emergency, Luigi Vanvitelli university of Campania, naples, Italy *Corresponding author: Vincenzo Piccolo, unit of Dermatology, Luigi Van- vitelli university of Campania, Via Pansini 5, 80131 naples, Italy. E-mail: piccolo.vincenzo@gmail.com References 1. Boyd aS, neldner KH. Lichen planus. J am acad Dermatol 1991;25:593–619. 2. Errichetti E, Stinco g. Dermoscopy in general Dermatology: a Practi- cal Overview. Dermatol Ther (Heidelb) 2016;6:471–507. 3. Lallas a, Kyrgidis a, Tzellos Tg, apalla Z, Karakyriou E, Kara- tolias a, et al. accuracy of dermoscopic criteria for the diagnosis of psoriasis, dermatitis, lichen planus and pityriasis rosea. Br J Dermatol 2012;166:1198–205. 4. Happle R. The categories of cutaneous mosaicism: a proposed clas- sifcation. Am J Med Genet A 2016;170:452–9. 5. Happle R. Superimposed segmental manifestation of polygenic skin disorders. J am acad Dermatol 2007;57:690–9. Conficts of interest.—The authors certify that there is no confict of inter- est with any fnancial organization regarding the material discussed in the manuscript. Authors’ contributions.—All authors read and approved the fnal version of the manuscript. History.—Article frst published online: June 17, 2019. - Manuscript accept- ed: June 10, 2019. - manuscript received: april 18, 2019. Supplementary data.—for supplementary materials, please see the HTmL version of this article at www.minervamedica.it figure 1.—a) Light-brown papule on the sole of a 2-year-old child; B) yellowish papule on the sole of a 8 year-old child; C) pigmented papule on the sole of a 45 year-old man; D) dermoscopy of the papule of case 1a showing the presence of a linear cut-hair. a D B C COPYRIGHT © 2021 EDIZIONI MINERVA MEDICA This document is protected by international copyright laws. No additional reproduction is authorized. It is permitted for personal use to download and save only one fle and print only one copy of this Article. It is not permitted to make additional copies (either sporadically or systematically, either printed or electronic) of the Article for any purpose. 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