Correlation of Dermatopathologic Findings and Autoantibody Subtypes in Dermatomyositis

BACKGROUND: Dermatomyositis is an autoimmune disease characterized by heterogeneous clinical and histopathologic features. Myositis-specific antibodies and myositis-associated antibodies have been linked to distinct clinical phenotypes, but their relationship with specific histopathologic features is unclear. This study aimed to characterize cutaneous histologic patterns in dermatomyositis patients with known autoantibody profiles. METHODS: We conducted a retrospective review of patients with positive myositis-specific antibody/myositis-associated antibody serology, a clinical diagnosis of dermatomyositis, and skin biopsies of lesional dermatomyositis-affected skin. Clinical data were extracted from medical records, and histopathologic features were recorded after masked review by 3 subspecialized dermatopathologists. Associations between antibody subtypes and histopathologic features were analyzed using Fisher exact test. RESULTS: The cohort comprised 30 patients who underwent 47 biopsies between 2009 and 2024. The most prevalent features were vacuolar interface dermatitis (70.4%), dermal mucin (71.1%), and mild superficial perivascular inflammation (81.5%). Perivascular inflammation without associated interface dermatitis was associated with nuclear matrix protein 2 positivity ( P < 0.01). Transcriptional intermediary factor 1γ-positive biopsies were less likely to demonstrate dermal mucin ( P < 0.01). No significant associations were found between antibodies and adnexal inflammation or the type of interface dermatitis (vacuolar or lichenoid). CONCLUSIONS: Variability in skin biopsy findings from dermatomyositis patients with specific autoantibodies is limited. Perivascular inflammation without interface change and an absence of dermal mucin may be more common in patients with nuclear matrix protein 2 and TIF1γ autoantibodies, respectively. These observations may aid diagnosis in cases with atypical histologic features.