Dermatology: Practical and Conceptual Image Letter | Dermatol Pract Concept. 2025;15(4):5243 1 Dermatomyositis-Like Lesion: An Atypical Cutaneous Presentation in Adult-Onset Still Disease Shirui Chen1, Lin Li1, Liming Xiang1, Xia Chen1, Cunhuo Jiang1 1 Department of Dermatovenereology, Chengdu Second People’s Hospital, Chengdu, Sichuan, China Citation: Chen S, Li L, Xiang L, Chen X, Jiang C. Dermatomyositis-Like Lesion: an Atypical Cutaneous Presentation in Adult-Onset Still Disease. Dermatol Pract Concept. 2025;15(4):5243. DOI: https://doi.org/10.5826/dpc.1504a5243 Accepted: June 4, 2025; Published: October 2025 Copyright: ©2025 Chen 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: Cunhuo Jiang, Department of Dermatovenereology, Chengdu Second People’s Hospital, Chengdu, Sichuan, China. E-mail: 527842348@qq.com Case Presentation A 56-year-old female with no prior dermatological history presented with persistent pruritic erythematous scaly plaques accompanied by fever, myalgia, and generalized lymphade- nopathy for over 20 days. The rash had started on the neck and chest and had rapidly spread to the face, back, and thighs (Figure 1A-D). Histopathology found dyskeratotic keratino- cytes of the upper third of epidermis. Muscle, bone marrow lymph node biopsies, and PET-CT found no substantial abnor- mality. The patient was initially diagnosed as having derma- tomyositis. However, based on Yamaguchi criteria, especially the highly specific and sensitive skin histopathology, clinical presentation and subsequent examinations, the final diagno- sis was adjusted to adult-onset Still’s disease (AOSD). During our 10-month follow-up after treatment with glucocorticoids and siltuximab, laboratory results, including complete blood count, liver function, and ferritin levels, showed improve- ment; the patient no longer had fever or any discomfort. Teaching Point AOSD is a rare systemic inflammatory disease with diverse clinical presentations. Skin rash is a key feature, which is typically characterized as evanescent, non-pruritic eruption, and often followed by spiking fever[1]. Here, we report an atypical case of AOSD with persistent pruritic dark-red le- sions on the face, neck, chest, and back, which are frequently associated with poor prognosis[2]. Dyskeratotic cells of the upper-to-mid-epidermis in histopathology is a crucial clue for diagnosis (Figure 1E). Dermatomyositis is the primary disease for differential diagnosis, and hematologic ma- lignancies should be ruled out. Early recognition of these clinical and pathological signs can aid in timely clinical decision-making. 2 Image Letter | Dermatol Pract Concept. 2025;15(4):5243 Reference 1. Mitrovic S, Fautrel B. Clinical Phenotypes of Adult-Onset Still's Disease: New Insights from Pathophysiology and Literature Findings. J Clin Med. 2021;10(12):2633. Published 2021 Jun 15. DOI:10.3390/jcm10122633. PMID: 34203779 2. Sun NZ, Brezinski EA, Berliner J, et al. Updates in adult-onset Still disease: Atypical cutaneous manifestations and associations with delayed malignancy.  J Am Acad Dermatol. 2015;73(2): 294-303. DOI:10.1016/j.jaad.2015.04.063. PMID: 26054431. Figure 1. (A-D) The patient presented erythema scale rash on the forehead, face, chest, back, and lateral thigh. (E) Histopathology found several dyskeratotic keratinocytes of the upper third of the epidermis and a few infiltra- tions of lymphocytes, neutrophils, and eosinophils in the superficial dermis (H&E, 400x).