Patients with JDM desperately need better treatments. Relatively little is known about the predictors of disease course and few proven treatment options exist. This ABC grant will allow the collection of precious biosamples in JDM with skin disease, along with precious CARRA Registry data. This project will allow for collaborative research that is now possible through the “Translational Medicine for Juvenile Myositis” Working Group in the CARRA JDM Disease Committee. With this infrastructure, we bring together the clinical and scientific expertise from multiple institutions, existing, well-described and longitudinal biosamples, and the systems biology analysis skills to carry out this proposed research. This will improve understanding of the biological heterogeneity of treatment response in JDM with skin disease, define candidate molecular biomarkers for prediction of treatment response, and characterize specific immunologic pathways that can be targeted for treatment in patient subgroups.