Belimumab, a monoclonal antibody against the soluble counterpart of B cell activating factor (BAFF), also known as B lymphocyte stimulator (BLyS), is used for the treatment of active systemic lupus erythematosus (SLE) despite standard of care therapy, that is, antimalarial agents and non-selective immunosuppressants including glucocorticoids [1]. This evidence concerns the gene TNFSF13B and systemic lupus erythematosus.