Dermatology: Practical and Conceptual Image Letter | Dermatol Pract Concept. 2023;13(3):e2023150 1 Brownish-Yellow Dots as a Dermoscopic Sign of Follicular Mucinosis Javier de la Iglesia Martin1, Jaime Piquero-Casals2, Angels Quera3, Daniel Morgado-Carrasco1,3 1 Dermatology Department, Hospital Clínic de Barcelona, Universitat de Barcelona, Barcelona, Spain 2 Dermik, Clínica Dermatológica Multidisciplinar, Barcelona, Spain 3 Dermatology Department, Hospital de Figueres, Fundació Salut Empordà, Girona, Spain Citation: de la Iglesia Martin J, Piquero-Casals J, Quera A, Morgado-Carrasco D. Brownish-Yellow Dots as a Dermoscopic Sign of Follicular Mucinosis Dermatol Pract Concept. 2023;13(3):e2023150. DOI: https://doi.org/10.5826/dpc.1303a150 Accepted: January 14, 2023; Published: July 2023 Copyright: ©2023 de la Iglesia Martin 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: Daniel Morgado-Carrasco, Hospital clínic de Barcelona, Villarroel 170, Barcelona (08036), Tel. (+34) 935 464 710 Fax (+34) 935 464 729 Email: morgadodniel8@gmail.com Case Presentation A 40-year-old man presented with a 2-year history of well defined, erythematous and alopecic plaques, together with alopecic patches on both shins. Dermoscopy showed medium-size brownish-yellow dots, arboriform vessels and patchy homogenous ivory-white areas (Figure 1). Laboratory tests including blood count, antinuclear antibodies, Ro/La antibodies, thyroid function and serum protein electropho- resis, together with serologies for syphilis, Lyme disease, hepatitis B and C virus, and HIV, and chest X-ray were nor- mal or negative. A punch biopsy revealed a follicular and perifollicular lymphocytic infiltrate with no cellular atypia, and deposition of an amorphic substance around follicles in the dermis. Alcian blue at pH 2.5 confirmed the presence of mucin (Figure 2). Based on clinicopathological characteris- tics a diagnosis of follicular mucinosis was made. Topical corticosteroids and hydroxychloroquine 400 mg/day were started, and long-term follow-up was recommended. Teaching Point Follicular mucinosis is a rare inflammatory dermatosis characterized by abnormal deposition of mucin on hair fol- licles [1]. There are two subtypes: idiopathic and associated with cutaneous lymphomas or hematological malignancies. The diagnosis of follicular mucinosis can be challeng- ing. Dermoscopic features of follicular mucinosis have scarcely been described. Dermoscopy may reveal white homogenous patches surrounded by a yellow border, in- terfollicular red dots and the tooth paste sign1 (white ge- latinous material along hair shafts). Yamagishi et al Haga clic o pulse aquí para escribir texto. reported perifollicular medium-size brownish-yellow dots, which were also seen in 2 Image Letter | Dermatol Pract Concept. 2023;13(3):e2023150 our patient [2]. These structures can also be observed in dis- coid lupus erythematosus, among other dermatoses. Dermoscopy may be helpful in the diagnosis of follicular mucinosis, and medium-size brownish-yellow dots can be a novel dermoscopic sign. References 1. Mumford BP, Ryan A, Chong AH, Lasocki A. Follicular muci- nosis with novel dermoscopic finding: the toothpaste sign. Clin Exp Dermatol. 2022;47(5):969-970. DOI: 10.1111/ced.15083. PMID: 34978345. 2. Yamagishi H, Ota M, Nobeyama Y, Asahina A. Case of follic- ular mucinosis showing brownish yellow and red dots via der- moscopy. Clin Case Rep. 2022;10(5). DOI: 10.1002/ccr3.5815. PMID: 35600022. PMCID: PMC9109645. A B Figure 1. (A) Follicular mucinosis. Well-defined, erythematous alopecic plaques, and alopecic patches on both shins. (B)  Dermoscopy reveals multiple medium-size brownish-yellow dots, and arboriform vessels. Scattered homogenous white areas can also be seen. AA B Figure 2. (A) Histopathologic picture. Lymphocytic infiltrate and amorphic substance around hair follicles. No cellular atypia was seen. (B) Alcian blue at pH 2.5 confirmed the presence of mucin.