Systemic lupus erythematosus (SLE) is a complex disease characterised by a wide range of clinical manifestations and autoantibodies and virtually any manifestation is considered to be possible in patients with SLE. Classically the disease has a relapsing remitting course and is characterised by damage accrual, increased morbidity and mortality, comorbidities. Early recognition of the disease could allow early intervention, prevent damage accrual and improve long term outcomes. However, the disease onset may be insidious, with clinically evident disease developing over years, and this can delay both the diagnosis and the classification of SLE; in addition some patients presenting with signs and symptoms of systemic autoimmune diseases will never develop SLE but will remain undifferentiated over time (UCTD, undifferentiated connective tissue diseases). Finally many different conditions may mimic SLE. Classification is required to include patients in clinical trials and these difficulties suggest the need for classification criteria able to classify early disease. The existing classification criteria (ACR and SLICC) appear to have a lower specificity in early disease, with an increase after 5 years of disease. New classification criteria for SLE have been developed to define a threshold above which experts could classify SLE for the purpose of research.1-4 Clinical and serological characteristics of early SLE patients compared with mimicking diseases, were identified to inform the development of these criteria with the specific aim to develop classification criteria able to capture patients in the early disease. Learning objectives Describe the variability of the clinical picture of SLE and describe the characteristics of early SLE Highlight the difficulties for early diagnosis of SLE Differentiate early SLE from mimicking conditions Discuss the development of the new EULAR/ACR criteria and their performance in early SLE References Johnson SR, Khanna D, Daikh D, et al. Use of Consensus Methodology to Determine Candidate Items for Systemic Lupus Erythematosus Classification Criteria. J Rheumatol 2019;46(7):721–26. Tedeschi SK, Johnson SR, Boumpas DT, et al. Multicriteria decision analysis process to develop new classification criteria for systemic lupus erythematosus. Ann Rheum Dis 2019;78(5):634–40. Mosca M, Costenbader KH, Johnson SR, et al. Brief Report: How Do Patients With Newly Diagnosed Systemic Lupus Erythematosus Present? A Multicenter Cohort of Early Systemic Lupus Erythematosus to Inform the Development of New Classification Criteria. Arthritis & rheumatology (Hoboken, NJ) 2019;71(1):91–98. Tedeschi SK, Johnson SR, Boumpas D, et al. Developing and Refining New Candidate Criteria for Systemic Lupus Erythematosus Classification: An International Collaboration. Arthritis care & research 2018;70(4):571–81.