Juvenile dermatomyositis is a disorder of skin, muscles, and blood vessels characterized by erythematous and oedematous changes in the skin associated with muscle weakness and inflammation. The objective of this study is to investigate whether the changes in membrane expression of cluster differentiation antigen on the surface of different lymphocyte subsets such as (CD3, 4, 8, and 19) and the Fas antigen correlate with disease activity. So fifteen patients, according to Peter and Bohan criteria, will be included during activity and after remission by analysis of blood by Flow Cytometry.