Longitudinal brush pigmentation on the hyponychium, a dermoscopic feature observed in pediatric nail matrix nevi

To the Editor: Differentiating nail matrix nevus (NMN) from subungual melanoma on clinical grounds is challenging, especially in children, because their NMNs may mimic features of melanoma.1Cooper C. Arva N.C. Lee et al.A clinical, histopathologic, and outcome study melanonychia striata childhood.J Am Acad Dermatol. 2015; 72: 773-779Abstract Full Text PDF PubMed Scopus (47) Google Scholar, 2Ohn J. Choe Y.S. Mun J.H. Dermoscopic adults children: a comparative analysis.J 2016; 75: 535-540Abstract (39) 3Lee Lim Y. Park al.Clinicopathologic 28 cases nevi (NMNs) Asians: comparison between children adults.J 2018; 78: 479-489Abstract (25) Scholar We reported dermoscopically linear parallel pigmentation longitudinal direction Hutchinson sign hyponychium with NMN.3Lee named this pattern brush (LBP) consider it distinctive dermoscopic feature observed pediatric NMN. further support this, we present dermoscopic, histologic hyponychial LBP associated additional 15 2014 2019. Biopsy specimens were performed 14 patients biopsy specimen 1 patient. All showed at hyponychium, brown lines that are perpendicular to skin groove, like (Fig 1; images all can be seen Supplemental Fig available via Mendeley https://data.mendeley.com/datasets/smj68n5xrt/1). Demographic data shown Table I. The mean age onset was 25 months width 54.3% total width. Five had dystrophy (33.3%). Six developed during follow-up remaining 9 already presented initial visit our clinic. average time development 27.5 months. Irregular including color variegation inconsistency globular 6 children.Table IDemographic casesPatient no.Age onset, moSexAffected nail∗The first letter specifies right (R) or left (L), last finger (F) toe (T). A number them indicates which affected.Width (% width)Nail dystrophyTime LBP, moLength follow-up, mo14MR5F100−14412<1ML1F33.3−LBP visit3338ML4F66.7+563042ML1F39.5+LBP visit13536FL1F72.7+LBP visit146<1FL3T52.4−LBP visit42771FR4F25−LBP visit24824MR1T100−2924936MR2T48−LBP visit81060FR3F100−LBP visit9115FL1F71.2+31271240MR2F29.6+LBP visit61380ML1T40.3−LBP visit171411FL1F13.1−1828153FL3F22.8−1730F, Female; pigmentation; M, male.∗ affected. Open table new tab F, male. Eleven punch nested proliferation banal melanocytes (Supplemental 2). 3 revealed solitary predominantly along dermoepidermal junction without atypia. One case some atypical cells but growth subsequent serial sections Although larger studies correlating findings those needed, observation benign supported impression NMN cases. suggest presence consistent process who otherwise lack more concerning clinicodermoscopic worrisome history. Conservative management through long-term still an option for such patients, being closely followed over long term. However, obtaining warranted clinically despite LBP. Any (including LBP) adult should prompt consideration matrix. In conclusion, underscore importance examination entire unit, melanonychia. propose its supports patients. None disclosed.