HK1 and arthritic joint disease: These findings include the facts that: anti-citrullinated protein autoantibodies can predate the development of clinical arthritis and provide a sensitivity of approximately 70% and a specificity of 97% for the diagnosis of RA [7,11,12,31]; anti-CD20-mediated B cell depletion provides efficacy in treating RA [9]; and the K/BxN mouse model develops spontaneous arthritis mediated by antibodies targeting the ubiquitous glycolytic enzyme GPI [32].