The presence of meningeal B-cell follicles is thought to play an important role in clinical progression of MS.14,26 One study showed that CXCL13 continuously increases in progressive MS suggesting that CXCL13 correlates with clinical progression.27 However, more prospective studies are still necessary to assess the role of CXCL13 in MS prognostic evaluation. The gene discussed is CXCL13; the disease is myeloid sarcoma.