Heterogeneity of Juvenile Dermatomyositis Based on Clinical Subtypes: An Exploratory Retrospective Study of Imaging, Clinical Manifestations, and Laboratory Profiles

Objective This exploratory retrospective study aimed to characterize the clinical, imaging, and serological profiles of juvenile dermatomyositis (JDM) patients and to explore potential associations across phenotypic subgroups. Methods In this exploratory study, 18 JDM patients were classified into three observed clinical subgroups according to skin, muscle, and systemic involvement at diagnosis. Demographic, imaging, clinical, and laboratory data were compared among subgroups. Results Mean age at diagnosis was 5.8 ± 3.6 years, with female predominance (male‐to‐female ratio of 1:3.5). Patients were classified into three groups: Group 1 ( n = 5, skin‐predominant), Group 2 ( n = 11, classic JDM), and Group 3 ( n = 2, overlap syndrome). Age at diagnosis differed significantly among groups. The incidence rates of Heliotrope rash and Gottron’s sign did not differ significantly across subgroups. Muscle edema was present in 15 patients (83.3%) overall, but its frequency was significantly higher in Groups 2 and 3 (100%) compared to Group 1 (40%). Interstitial lung disease (ILD) was identified in five cases (27.8%), including one case in Group 1 and four cases in Group 2. Calcinosis was observed in three cases (16.7%), two of whom had concurrent ILD. Articular involvement was observed in five cases (27.8%), distributed in Group 2 (27.3%) and Group 3 (100%). Muscle weakness was universal in Groups 2 and 3 (100%); its overall incidence was lower than that of muscle edema. Elevation in muscle enzymes and cardiac markers were confined to Group 2. ANA positivity was common (61.1%). Anti‐MDA5 and anti‐NXP2 antibodies were each detected in two patients and appeared to be associated with ILD and calcinosis, respectively. Anti‐SSA/Ro52 and Ro60 antibodies were found in five cases, including one dual‐positive patient in Group 3. Conclusion This exploratory retrospective study suggests that JDM comprises clinically heterogeneous phenotypic subgroups with significant differences in imaging, clinical, and laboratory findings. A comprehensive evaluation is recommended for every JDM patient to clarify organ involvement and guide timely management. These results highlight the heterogeneity of JDM.