Systemic lupus erythematosus (SLE) characterizes by a variety of clinical manifestations and the presence of a wide profile of autoantibodies. This clinical and serological heterogeneity raised the question: is SLE a single disease with varied phenotypes, or a similar phenotype shared by different diseases with diverse pathogenic mechanisms? Herein we debate the clinical, genetic, hormonal and serological differences typically observed in SLE on the one hand, and the numerous similarities between subtypes of this disease on the other. Leading to the conclusion that SLE may be considered not as a single disease but rather as a single syndrome, which defines by a set of signs, symptoms, or phenomena that occur together and suggest a particular abnormality. Additionally, the accumulated knowledge on gene expression pathways, autoantibodies clusters, hormonal and environmental factors associated with SLE may allow a better classification of this syndrome and updating of SLE criteria. This may further allow targeted biologics and other therapies as well as "personalized medicine" to begin. Copyright © 2011 Elsevier B.V. All rights reserved.