Classification of systemic lupus erythematosus: From the development of classification criteria to a new taxonomy?

SLE is a highly variable systemic autoimmune disease. Its immunopathological effector phase is partly understood. However, the background of its variability is not. SLE classification criteria have been relying on the clinical manifestations and standard autoimmune serology. This still holds true for the 2019 EULAR/ACR classification criteria. On one hand, this has led to significant precision in defining patients with SLE. On the other hand, the information in the criteria neither helps understanding the individual patient's pathophysiology, nor does it predict the efficacy of the available immunomodulatory therapies. Chances of further improvement of clinical criteria are most likely limited. This is where new multi-omic approaches have started to make an impact. While not yet able to differentiate diseases with the same precision as the classification criteria, the results of these studies go far beyond the scope of the criteria with regard to immune dysregulation. Looking at both sides in detail, we here try to synthesize the available data, aiming at a better understanding of SLE and its immune pathophysiology.