[Definition, diagnosis, and classification of lupus]

Polysystemic lupus erythematosus is a disease of unclear origin. Spontaneous course is characterized by flares followed by remissions. The classification criteria are often used as diagnostic criteria, but they are insensitive for early diagnosis purpose. Decisional trees and ponderation of the various criteria have been reported to help clinicians for early diagnosis. Clinical variants of lupus erythematosus are numerous such as initial clinical manifestations; epidemiological considerations have shown different subsets with different manifestations depending on ethnicity, age at first symptoms, environmental factors (drug-induced lupus). Genetic background influences the autoantibody profile. Correlations have been reported between serological and clinical presentation.