Early recognition followed by treatment of rheumatoid arthritis (RA) helps to maintain joint integrity and functional capacity,1 suggesting it may be beneficial to intervene in patients with arthralgia before RA develops. Anticitrullinated protein antibodies (ACPA) and rheumatoid factor (RF) are established predictive markers,2 ,3 but only 20–40% of ACPA and/or RF positive patients with arthralgia develop RA within 2 years.4 Recently, we have demonstrated that the type I interferon (IFN) signature correctly identifies 52% of patients with arthralgia who will develop RA within 2 years.5 ,6 Our previous study suggested that a B cell related gene signature was associated with protection against arthritis development,6 and could aid in the prediction of arthritis development. We therefore studied the clinical value of the B cell signature, comprising CD19, CD20, CD79α and CD79β, for the prediction of arthritis development in an independent cohort of 115 ACPA and/or RF positive patients with arthralgia followed for median 22 months5 and explored the phenotypical nature of this B cell signature. In total, 44 patients (38%) developed arthritis (defined as one or more swollen joints) within 2 years. Of these, 4 patients had undifferentiated arthritis and 40 patients fulfilled the 2010 American College of Rheumatology (ACR)/ European League Against Rheumatism (EULAR) criteria for RA. Patients were stratified into B cell^{high …}