BAFF adds to the evolving picture of B-cell involvement in OMS, which includes CSF B-cell subset expansion [2], positive oligoclonal bands [5], intrathecal over-production of CXCL13 [3], selective over-expression of CXCR5 receptors on CSF memory B cells [3], and clinical response to adjunctive anti-CD20 monoclonal antibody rituximab [1]. The gene discussed is CXCR5; the disease is opsoclonus-myoclonus syndrome.