Compared to HC, CIS/eRRMS having IgGOB (IgGOB+, 26 patients) had higher intrathecal IgG indexes (p < 0.01), lower values of BAFF Index (11.9 ± 6.1 vs 17.5 ± 5.2, p < 0.01), and higher CSF CXCL13 levels (27.7 ± 33.5 vs 0.9 ± 1.5, p < 0.005). Here, CXCL13 is linked to in situ carcinoma.