Background SLE is a heterogeneous disease with diverse clinical presentations, and up to 70–80% of patients develop skin manifestations. 1–3 In SLE, plasmacytoid dendritic cells (pDCs), major source Type I interferon (IFN), accumulate in the skin. 4 Treatment BIIB059, humanized monoclonal antibody targeting blood cell antigen 2 (BDCA2) that expressed on pDCs, leads rapid internalization BDCA2 f...