Dermatology: Practical and Conceptual Image Letter | Dermatol Pract Concept. 2023;13(4):e2023208 1 Nail Lichen Striatus Affecting Adjacent Nails: A Sign of Blaschko Lines Laura Gnesotto1, Guido Mioso1, Michela Starace2, Bianca Maria Piraccini2, Luigi Naldi3, Andrea Sechi2,3 1 Department of Medicine-DIMED, Unit of Dermatology, University of Padova, Padova, Italy 2 Division of Dermatology, Department of Experimental, Diagnostic and Specialty Medicine, University of Bologna, Bologna, Italy 3 Dermatology Unit, San Bortolo Hospital, Vicenza, Italy Citation: Gnesotto L, Mioso G, Starace M, Piraccini BM, Naldi L, Sechi A. Nail Lichen Striatus Affecting Adjacent Nails: A Sign of Blaschko Lines. Dermatol Pract Concept. 2023;13(4):e2023208. DOI: https://doi.org/10.5826/dpc.1304a208 Accepted: March 28, 2023; Published: October 2023 Copyright: ©2023 Gnesotto 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: Andrea Sechi, Dermatology Unit, San Bortolo Hospital, Vicenza, Italy. E-mail: andrea.sechi@aulss8.veneto.it Case Presentation A 5-year-old boy presented a 10-month history of an asymp- tomatic linear eruption affecting the later aspects of his left index and medial surface of the medium finger, which had gradually spread to the periungual skin, the nail bed and matrix causing an acquired nail plate dystrophy. Physical ex- amination revealed multiple pinkish and hyperkeratotic pap- ules of the affected digits associated with mild erythema of proximal nail folds. The two nail plates were only partially involved, showing longitudinal splitting and ridging associ- ated with splitting and hyperkeratosis of the distal margin (Figure  1A). Onychoscopy enhanced the detection of the longitudinal streak, distal splitting, punctiform and splinter hemorrhages in the nail bed (Figure 1B). The skin papules tended to coalesce near the proximal nail folds, displaying a reticular white-yellowish structure with fine scales and peripheral radial capillaries (Figure 1C). Based on clinical findings, a diagnosis of lichen striatus (LS) was posed. The patient was treated with topical mometasone furoate 0.1% cream twice a day for three months, leading to complete resolution of skin lesions; nail changes resolved completely within one year with no recurrence. Teaching Point The involvement of the nail unit in LS is rare and generally localized to a single nail, either or not in association with cutaneous lesions [1,2]. The involvement of two adjacent nail plates reminds us of its blaschkoid distribution, a diag- nostic clue of LS. Dermoscopy reveals distinctive features of nail LS, such as longitudinal white-yellowish streaks or lines parallel to the nail bed, interrupted by hyperkeratosis. These findings help to avoid unnecessary biopsies, given the disor- der’s positive prognosis. 2 Image Letter | Dermatol Pract Concept. 2023;13(4):e2023208 References 1. Kavak A, Kutluay L. Nail involvement in lichen striatus. Pediatr Dermatol. 2002;19(2):136-138. DOI: 10.1046/j.1525 -1470.2002.00049.x. PMID: 11994177. Figure 1. Nail lichen striatus. (A) Clinical presentation: multiple pinkish papules with blas- hkoid distribution, affecting the left index and medium finger with partial involvement of the two adjacent nail plates. (B) Onychoscopy reveals longitudinal ridging, distal splitting and splinter hemorrhages in the nail bed. (C) Dermoscopy of skin papules shows a slight erythematous background and reticular white-yellowish structure covered with whitish scales. 2. Kim M, Jung HY, Eun YS, Cho BK, Park HJ. Nail lichen striatus: report of seven cases and review of the literature. Int J Derma- tol. 2015;54(11):1255-1260. DOI: 10.1111/ijd.12643. PMID: 26474189.